This cohort study estimates the global incidence and outcomes of in-flight medical events on commercial airline flights.
Key Points
Question
What are the characteristics of in-flight medical events on commercial airline flights and the factors associated with aircraft diversion, hospital transport, and in-flight mortality?
Findings
In this cohort study of 77 790 in-flight medical events reported by 84 airlines, the overall incidence was 39 per 1 million enplanements, and aircraft diversion occurred in 1.7% of cases, most often for neurologic and cardiac emergencies. Physician volunteer involvement was associated with increased likelihood of diversion.
Meaning
The findings suggest that in-flight medical events are more common than previously estimated and have important operational and clinical implications for commercial aviation and emergency response planning.
Abstract
Importance
In-flight medical events are an inevitable challenge in commercial aviation. Managing these events is complicated by constrained medical resources and delayed access to definitive care.
Objective
To characterize the epidemiology of in-flight medical events and identify factors associated with aircraft diversion, hospital transport, and in-flight mortality.
Design, Setting, and Participants
This cohort study included 77 790 in-flight medical events reported to a global ground-based medical support center from January 1, 2022, through December 31, 2023. All passengers experiencing an in-flight medical event across 84 participating airlines during the study period were included. Data were collected from consultations initiated by flight crew via radio or satellite communication with a dedicated ground-based physician. No demographic or clinical exclusions were applied.
Exposures
Medical conditions occurring during commercial flights that prompted contact with the ground-based support center. Data included clinical presentation, in-flight management, passenger demographics, involvement of volunteer medical professionals, and disposition.
Main Outcomes and Measures
Primary outcome was aircraft diversion, and secondary outcomes were hospital transport and in-flight mortality. Descriptive statistics, univariate analyses, and multivariable analyses were used to identify clinical and operational variables associated with these outcomes.
Results
Among 77 790 in-flight medical events, the overall incidence was 39 events per 1 million enplanements, with 1 event per 212 flights, or 17 events per billion revenue passenger kilometers. The median (IQR) age of affected passengers (42 316 females [54.4%]) was 43 (27-61) years. Aircraft diversion occurred in 1.7% of cases, most frequently due to neurologic (41%) and cardiovascular (27%) conditions. Suspected stroke (adjusted OR [AOR], 20.35; 95% CI, 12.98-31.91) and acute cardiac emergencies (AOR, 8.16; 95% CI, 6.38-10.42) were the factors associated with the highest odds of diversion. The involvement of a physician volunteer was also associated with increased odds of diversion (AOR, 7.86; 95% CI, 4.49-13.78).
Conclusions and Relevance
In this cohort study of 77 790 in-flight medical events, these events occur more frequently than previously reported. Serious neurologic conditions, cardiac events, and physician volunteer involvement are each associated with higher odds of diversion. These findings contribute to the understanding of in-flight medical event frequency and outcomes and may inform policy, flight crew training, and diversion protocols.
Introduction
Commercial air travel is a cornerstone of global connectivity, with nearly 5 billion passengers projected to fly in 2025.1 As the number of enplanements continues to rise, so does the likelihood of an in-flight medical emergency—occurring in an environment where resources are limited and access to definitive care is delayed.2 Flight crew trained in first aid may provide very basic initial care, while medically trained passengers may be asked to assist in select situations.3 Increasingly, airlines also rely on real-time consultation with ground-based medical support centers to help guide in-flight medical decision-making.2
While serious in-flight medical events can and do occur, most events are of relatively low acuity.2,3 Still, data on their frequency, characteristics, management, and outcomes remain scarce. Prior studies have sought to characterize in-flight medical events, but most have been limited to single airlines or specific geographic regions, restricting generalizability.4,5,6,7,8,9,10,11,12,13,14 A landmark study10 published more than a decade ago provided valuable insight into in-flight medical events on 5 airlines assisted by a US-based medical support center; however, no comprehensive, large-scale multinational study has evaluated these events on a truly global scale. This study aims to provide a comprehensive characterization of in-flight medical events across global commercial air travel, using a large multinational dataset to examine their epidemiology, resource utilization, and outcomes.
Methods
Study Design and Data Source
We conducted an observational cohort study of in-flight medical events on commercial airline flights between January 1, 2022, and December 31, 2023. Source data were obtained through queries of MedAire’s clinical database, a global ground-based support center delivering specialized real-time medical guidance to more than 100 airlines from 5 continents, representing approximately 31% of worldwide commercial air traffic during the study period. Located at a level I trauma center in the US, the medical support center is staffed continuously by onsite, dedicated practicing emergency medicine physicians with expertise in telemedicine, airline protocols, and flight physiology. These specifically assigned clinicians are tasked with providing immediate guidance to the flight crew or passenger volunteers; they have knowledge of the contents of the specific airline emergency medical kits and are trained to manage medical emergencies across the entire age spectrum. This study was conducted under the oversight of the institutional review board at Duke University and was deemed exempt from review and the informed consent requirement due to the deidentified nature of the dataset. This study follows the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline.
The deidentified dataset used in this study was abstracted from structured and contemporaneously generated electronic records of all in-flight medical events reported to the ground-based medical support center during the period of interest. Events that occurred after aircraft door closure but before takeoff (ground returns) and those involving crew members were excluded.
Enplanement counts, defined as a passenger boarding an aircraft for a flight segment, were used for the entire airline cohort to calculate the rate of in-flight medical events per 1 million passengers. To account for exposure differences between long and short flights, we also report rates of in-flight medical events per billion revenue passenger kilometers (RPKs). To calculate the incidence of in-flight medical events relative to the total number of flights, we conducted a subanalysis using a restricted sample of 9 US-based carriers and their regional subsidiaries for which publicly accessible flight activity data were available, as precise flight counts were not obtainable for the entire cohort.15
Data Collection and Variables
At the discretion of crew members, satellite or radio communication was used to connect onboard personnel or passenger volunteers with the ground-based medical support center. Each call generated a structured electronic record in real time, capturing details of the medical issue, diagnostic impressions, management recommendations, and immediate outcomes. Free-text narrative summaries from each record provided additional clinical context when necessary. For this study, we defined fight distance using the following categories: short haul (<1500 km), medium haul (1500 to 3999 km), long haul (4000 to 12 000 km), and ultra-long haul (>12 000 km).
Outcomes
The primary outcome was aircraft diversion due to a medical emergency. The secondary outcomes were transport to a hospital on landing and in-flight death. Diversion decisions were not protocolized. While input from the ground-based physician and onboard medical volunteers was typically sought, the final decision to divert rested with the aircraft captain and was influenced by a combination of medical, operational, and logistical factors.
Statistical Analysis
We analyzed data using R, version 4.4.2 (R Foundation for Statistical Computing) within RStudio, version 2024.12.0 build 467 (Posit Software PBC). We summarized categorical variables as frequencies and percentages, and continuous variables as medians with IQRs. We conducted univariate and multivariable logistic regression analyses to assess factors associated with the primary outcome (aircraft diversion) as well as transport to a hospital and death. We selected candidate variables a priori to develop models that were both parsimonious and clinically relevant. These variables were age, flight distance, volunteer medical professional, and select diagnoses. To account for potential clustering by airline, we calculated robust SEs clustered at the airline level, which adjusts for intra-cluster correlation when random intercepts are not estimable for all outcomes. Prior to model fitting, we evaluated the linearity of continuous variables with respect to the log odds of the outcome using Box-Tidwell tests; multicollinearity using variance inflation factors; and the role of individual data points using diagnostic measures, such as Cook’s distance, leverage values, and standardized residuals. A 2-sided P < .05 was considered significant. We present these results as unadjusted odds ratios (ORs) and adjusted odds ratios (AORs) with robust 95% CIs.
Results
During the study period, 77 790 in-flight medical events across 84 airlines were reported to the ground-based medical support center and were included in the analysis. The median (IQR) age of involved passengers (42 316 women [54.4%], 33 142 men [42.6%], 2 nonbinary [<0.1%]) was 43 (27-61) years, and most incidents involved female passengers (Table 1). Most reported events occurred on international flights (52 594 [67.6%]), with long-haul routes (38 599 [49.6%]) accounting for the largest proportion.
Table 1. Characteristics of In-Flight Medical Events by Outcome.
| Characteristic | Outcome, No. (%) | |||
|---|---|---|---|---|
| Total (N = 77 790) | Aircraft diverted (n = 1333) | Transported to hospital (n = 5959) | Died (n = 312) | |
| Age, median (IQR), y | 43 (27-61) | 56 (40-70) | 53 (35-68) | 69 (55-79) |
| Missing data | 5342 | 193 | 548 | 57 |
| Gender | ||||
| Female | 42 316 (54.4) | 555 (41.6) | 2957 (49.6) | 129 (41.3) |
| Male | 33 142 (42.6) | 717 (53.8) | 2818 (47.3) | 169 (54.1) |
| Nonbinary | 2 (<0.1) | 0 | 0 | 0 |
| Missing data | 2330 | 61 | 184 | 14 |
| Year | ||||
| 2022 | 32 836 (42.2) | 593 (44.5) | 2326 (39.0) | 132 (42.3) |
| 2023 | 44 954 (57.8) | 740 (55.5) | 3633 (61.0) | 180 (57.7) |
| Route | ||||
| International | 52 594 (67.6) | 738 (55.4) | 3033 (50.9) | 231 (74.0) |
| Domestic | 25 196 (32.4) | 595 (44.6) | 2926 (49.1) | 81 (26.0) |
| Aircraft type | ||||
| Wide body | 40 765 (53.5) | 527 (40.4) | 2111 (36.0) | 190 (62.9) |
| Narrow body | 35 444 (46.5) | 777 (59.6) | 3745 (64.0) | 112 (37.1) |
| Missing data | 1581 | 29 | 103 | 10 |
| Flight distance (km) | ||||
| Short haul (<1500) | 4905 (6.3) | 86 (6.5) | 718 (12.0) | 16 (5.1) |
| Medium haul (1500-3999) | 30 258 (38.9) | 647 (48.5) | 3005 (50.4) | 101 (32.4) |
| Long haul (4000-12 000) | 38 599 (49.6) | 548 (41.1) | 2088 (35.0) | 174 (55.8) |
| Ultralong haul (>12 000) | 4028 (5.2) | 52 (3.9) | 148 (2.5) | 21 (6.7) |
| Volunteer medical professional | ||||
| Physician | 15 627 (20.1) | 729 (54.7) | 2028 (34.0) | 175 (56.1) |
| Nurse | 6556 (8.4) | 227 (17.0) | 824 (13.8) | 51 (16.3) |
| Paramedic or EMT | 1539 (2.0) | 49 (3.7) | 212 (3.6) | 8 (2.6) |
| Othera | 1713 (2.2) | 51 (3.8) | 205 (3.4) | 12 (3.8) |
| Missing data, | 135 | 0 | 2 | 0 |
| Additional care providedb | 51 790 (66.6) | 994 (74.6) | 4085 (68.6) | 297 (95.2) |
Abbreviation: EMT, emergency medical technician.
Including dentists, psychologists, nursing students, and medical students.
Defined as use of oxygen support; use of medical equipment kit; receipt of select medications; use of electrocardiogram; need for cardiopulmonary resuscitation or use of automated external defibrillator.
The incidence of in-flight medical events, diversions, and deaths relative to passenger enplanements, RPKs, and flights is shown in Table 2. In the worldwide sample, in-flight medical events occurred at a rate of 39 per 1 million passengers or 17 events per billion RPKs, while among the 9 US-based airlines and their regional subsidiaries, the incidence was 33 per 1 million passengers, 15 events per billion RPKs, or 1 event per 212 flights. The median (IQR) incidence of in-flight medical events was 1 per 199 (139-291) flights, with considerable variation among carriers, ranging from 1 per 114 flights to 1 per 480 flights.
Table 2. Incidence of In-Flight Medical Events Worldwide and in US-Based Airlines.
| Variable | Event rate | Median (IQR) | Range |
|---|---|---|---|
| Worldwidea | |||
| IMEs per 1 million enplanements | 39 | 34 (18-54) | 7-257 |
| Diversions per 1 million enplanements | 0.64 | 0.53 (0.31-0.73) | 0.00-1.73 |
| Deaths per 1 million enplanements | 0.15 | 0.12 (0.05-0.23) | 0.00-1.11 |
| IMEs per 1 billion RPK | 17 | 17 (10-26) | 2-50 |
| Diversions per 1 billion RPK | 0.28 | 0.22 (0.13-0.29) | 0.00-0.53 |
| Deaths per 1 billion RPK | 0.06 | 0.05 (0.02-0.09) | 0.00-0.35 |
| USb | |||
| IMEs per 1 million enplanements | 33 | 33 (28-54) | 14-65 |
| Diversions per 1 million enplanements | 0.86 | 0.67 (0.53-1.18) | 0.35-1.43 |
| Deaths per 1 million enplanements | 0.14 | 0.15 (0.06-0.23) | 0.05-0.53 |
| IMEs per 1 billion RPK | 15 | 19 (13-21) | 7-29 |
| Diversions per 1 billion RPK | 0.39 | 0.32 (0.26-0.53) | 0.21-0.63 |
| Deaths per 1 billion RPK | 0.06 | 0.07 (0.04-0.10) | 0.03-0.22 |
| Flights per IME | 212 | 199 (139-291) | 114-480 |
| Flights per diversion | 8138 | 10 606 (6278-12 822) | 4770-19 169 |
| Flights per death | 50 716 | 56 835 (30 074-109 764) | 14 518-138 972 |
Abbreviations: IME, in-flight medical event; RPK, revenue passenger kilometer.
Precise flight count information was not available for the worldwide cohort, so the ratios of flights per IME, diversion, or death are only shown for the US-based cohort.
US-based sample calculations are derived from 995 451 388 passengers transported on 6 998 868 flights by 9 US-based airlines and their regional subsidiaries.
Among all in-flight medical events, most (41 220 [53.0%]) involved in-flight advice and treatment only, requiring no further intervention upon landing; 12 263 (15.8%) patients were treated onsite and released, 5959 (7.7%) required transport to a hospital for further care, 4536 (5.8%) declined medical assistance, 312 (0.4%) died, and 13 500 (17.4%) had other dispositions (Figure). In this study, the phrase treated onsite and released refers to evaluation and management by airport-based medical personnel, typically paramedics or physicians, after landing, with a determination that the individual is stable enough to forgo hospital treatment.
Figure. Patient Disposition and Immediate Outcomes of the 77 790 Consultations for In-Flight Medical Events.
Other includes 11 952 cases with ambiguous disposition documentation, 745 cancelled requests, 284 dropped calls, 167 follow-ups with primary physician, 143 ground emergency medical services cancelled by crew, 37 consultations via app interface only, 6 cases notified postincident, and 166 cases with missing data.
Passenger volunteers with a medical background assisted in 25 570 events (32.9%) (Table 1), with physicians providing care in most of those cases. Medical volunteers were involved in 1056 diversions (79.2%) and 246 cases (78.9%) resulting in death. Events that were assisted by a physician were associated with higher odds of diversion compared with those involving other health care professionals (OR, 1.42; 95% CI, 1.24-1.62).
Aircraft diversion due to a medical emergency occurred in 1333 cases (1.7%). The median (IQR) age of passengers involved in aircraft diversion was 56 (40-70) years. The most common causes of diversion were neurological issues (542 [40.7%]) and cardiovascular conditions (359 [26.9%]) (eTable 1 in Supplement 1). In the univariate analysis, suspected stroke was associated with the highest odds of aircraft diversion (OR, 19.77; 95% CI, 15.36-25.44), followed by acute cardiac emergencies (OR, 9.21; 95% CI, 7.87-10.79), altered mental status (OR, 7.58; 95% CI, 6.93-8.98), and anaphylaxis (OR, 5.59; 95% CI, 2.92-10.74). Passengers experiencing a suspected stroke (OR, 6.59; 95% CI, 5.27-8.25), altered mental status (OR, 3.43; 95% CI, 3.03-3.88), or chest pain (OR, 3.07; 95% CI, 2.75-3.41) had the highest odds of being transported to a hospital on landing (eTable 2 in Supplement 1).
Medical Interventions and Passenger Outcomes
Oxygen therapy was the most frequent intervention and was used in 31 707 (40.8%) in-flight medical events, including in 842 (63.2%) cases resulting in aircraft diversion (Table 3). The medical equipment kit was reportedly accessed in 17 789 (22.9%) of cases, with nonnarcotic analgesics (11 788 [15.2%]) and antiemetics (11 624 [14.9%]) being the most frequently administered therapeutic classes.
Table 3. Additional Care Provided During In-Flight Medical Events According to Outcome.
| Treatment | Outcome, No. (%)a | |||
|---|---|---|---|---|
| All events (n = 77 790) | Aircraft diverted (n = 1333) | Transported to hospital (n = 5959) | Died (n = 312) | |
| Oxygen | 31 707 (40.8) | 842 (63.2) | 3119 (52.3) | 145 (46.5) |
| Medical equipment kit opened | 17 798 (22.9) | 297 (22.3) | 1333 (22.4) | 72 (23.1) |
| Medication agents used | ||||
| Nonnarcotic analgesic | 11 788 (15.2) | 105 (7.9) | 732 (12.3) | 5 (1.6) |
| Antiemetic | 11 624 (14.9) | 88 (6.6) | 632 (10.6) | 1 (0.3) |
| Antihistamine | 2662 (3.4) | 16 (1.2) | 105 (1.8) | 0 |
| Bronchodilator | 1781 (2.3) | 44 (3.3) | 217 (3.6) | 2 (0.6) |
| Antiplatelet | 1775 (2.3) | 110 (8.3) | 309 (5.2) | 7 (2.2) |
| Antispasmodic | 1475 (1.9) | 3 (0.2) | 46 (0.8) | 2 (0.6) |
| Narcotic analgesic | 1341 (1.7) | 12 (0.9) | 107 (1.8) | 1 (0.3) |
| Antidiarrheal | 1319 (1.7) | 1 (0.1) | 46 (0.8) | 0 |
| Burn aid | 954 (1.2) | 0 | 17 (0.3) | 0 |
| Antacid | 768 (1.0) | 6 (0.5) | 19 (0.3) | 0 |
| Intravenous fluid | 530 (0.7) | 76 (5.7) | 144 (2.4) | 10 (3.2) |
| Vasodilator | 519 (0.7) | 72 (5.4) | 157 (2.6) | 5 (1.6) |
| Anxiolytic | 463 (0.6) | 6 (0.5) | 26 (0.4) | 1 (0.3) |
| Antihypoglycemic | 312 (0.4) | 37 (2.8) | 78 (1.3) | 6 (1.9) |
| Anticonvulsant | 171 (0.2) | 14 (1.1) | 24 (0.4) | 0 |
| Adrenergic | 140 (0.2) | 23 (1.7) | 23 (0.4) | 32 (10.3) |
| Vasopressor | 100 (0.1) | 16 (1.2) | 16 (0.3) | 33 (10.6) |
| Corticosteroid | 64 (0.1) | 0 | 6 (0.1) | 0 |
| Antipsychotic | 26 (<0.1) | 0 | 4 (0.1) | 0 |
| Antiarrhythmic | 24 (<0.1) | 7 (0.5) | 5 (0.1) | 6 (1.9) |
| Opiate antagonist | 22 (<0.1) | 3 (0.2) | 8 (0.1) | 1 (0.3) |
| Diuretic | 17 (<0.1) | 2 (0.2) | 9 (0.2) | 0 |
| Antibiotic | 10 (<0.1) | 1 (0.1) | 3 (0.1) | 0 |
| CPR | 293 (0.4) | 123 (9.2) | 80 (1.3) | 276 (88.5) |
| AED shock applied | 42 (14.0) | 29 (23.6) | 19 (23.8) | 35 (12.7) |
Abbreviations: AED, automated external defibrillator; CPR, cardiopulmonary resuscitation.
Percentages may not add to 100 due to multiple treatments or rounding.
Cardiopulmonary resuscitation was performed in 293 cases (0.4%), with an automated external defibrillator shock delivered in 42 instances (Table 3). A total of 312 passengers (0.4%) died during the flight or were pronounced dead shortly after landing. The median (IQR) age of deceased passengers was 70 (60-78) years, with acute cardiac emergencies accounting for the majority of deaths (276 [88.5%]).
Multivariable Analyses of Outcomes
The factors with the highest odds of aircraft diversion were suspected stroke (AOR, 20.35; 95% CI, 12.98-31.91), acute cardiac emergency (AOR, 8.16; 95% CI, 6.38-10.42), and altered mental status (AOR, 6.96; 95% CI, 5.98-8.76) (Table 4). Greater odds of aircraft diversion were associated with ultralong-haul flights (AOR, 1.84; 95% CI, 1.19-2.84) and the involvement of a physician passenger volunteer (AOR, 7.86; 95% CI; 4.49-13.78). Suspected stroke (AOR, 4.48; 95% CI, 2.92-6.87) and seizure (AOR, 2.45; 95% CI, 1.93-3.11) were associated with subsequent transport to a hospital.
Table 4. Multivariable Analysis and Absolute Event Rates for Covariates Associated With Selected Outcomes.
| Covariate | Aircraft Diverted | Transported to Hospital | Died | |||
|---|---|---|---|---|---|---|
| Rate per 1000 covariate events | AOR (95% CI) | Rate per 1000 covariate events | AOR (95% CI) | Rate per 1000 covariate events | AOR (95% CI) | |
| Age, ya | NA | 1.01 (1.01-1.02) | NA | 1.01 (1.01-1.02) | NA | 1.00 (1.00-1.00) |
| Flight distance (km) | ||||||
| Short haul (<1500) | NA | 1 [Reference] | NA | 1 [Reference] | NA | 1 [Reference] |
| Medium haul (1500-3999) | 21.4 | 1.48 (1.09-2.00) | 99.3 | 0.64 (0.53-0.78) | 3.9 | 0.91 (0.52-1.60) |
| Long haul (4000-12 000) | 14.2 | 1.44 (0.97-2.14) | 54.1 | 0.38 (0.27-0.53) | 4.2 | 0.99 (0.58-1.68) |
| Ultralong haul (>12 000) | 12.9 | 1.84 (1.19-2.84) | 36.7 | 0.27 (0.17-0.43) | 4.0 | 0.92 (0.55-1.54) |
| Volunteer medical professional | ||||||
| None | NA | 1 [Reference] | NA | 1 [Reference] | NA | 1 [Reference] |
| Physician | 46.7 | 7.86 (4.49-13.78) | 129.8 | 2.41 (1.67-3.47) | 3.5 | 0.84 (0.64-1.10) |
| Nurse | 34.6 | 5.67 (3.32-9.68) | 125.7 | 2.05 (1.47-2.85) | 4.0 | 0.95 (0.67-1.34) |
| Paramedic or EMT | 31.8 | 5.24 (3.29-8.35) | 137.8 | 2.32 (1.67-3.24) | 2.6 | 0.51 (0.14-1.93) |
| Otherb | 29.8 | 4.28 (2.48-7.37) | 119.7 | 1.93 (1.40-2.66) | 6.4 | 1.76 (1.08-2.86) |
| Select diagnosesc | ||||||
| Otherd | NA | 1 [Reference] | NA | 1 [Reference] | NA | 1 [Reference] |
| Syncope or near syncope | 7.0 | 0.52 (0.42-0.65) | 52.1 | 0.54 (0.46-0.64) | 4.0 | 0.97 (0.73-1.27) |
| Dyspnea | 22.4 | 1.79 (1.28-2.50) | 113.5 | 1.20 (1.02-1.41) | 2.7 | 0.61 (0.28-1.33) |
| Seizure | 49.5 | 4.68 (3.84-5.71) | 170.6 | 2.45 (1.93-3.11) | 3.2 | 0.88 (0.54-1.44) |
| Abdominal pain | 13.7 | 1.97 (1.48-2.64) | 91.7 | 1.74 (1.44-2.10) | 5.4 | 1.28 (0.81-2.04) |
| Chest pain | 64.8 | 4.89 (4.01-5.97) | 194.9 | 2.33 (1.99-2.73) | 2.3 | 0.57 (0.25-1.29) |
| Acute cardiac emergency | 121.9 | 8.16 (6.38-10.42) | 173.6 | 1.87 (1.44-2.43) | 3.6 | 0.79 (0.31-2.06) |
| Altered mental status | 105.4 | 6.96 (5.98-8.11) | 214.6 | 2.40 (1.87-3.08) | 5.0 | 1.20 (0.60-2.42) |
| Suspected stroke | 244.9 | 20.35 (12.98-31.91) | 349.9 | 4.48 (2.92-6.87) | 2.9 | 0.78 (0.10-6.24) |
| Treatment | ||||||
| No oxygen | NA | 1 [Reference] | NA | 1 [Reference] | NA | 1 [Reference] |
| Oxygen | 26.6 | 1.59 (1.44-1.75) | 98.4 | 1.34 (1.20-1.50) | 4.1 | 1.09 (0.82-1.44) |
Abbreviations: AOR, adjusted odds ratio; EMT, emergency medical technician; NA, not applicable.
Age was analyzed as a continuous variable. An odds ratio of 1.01 suggests that each 1-year increase in age is associated with a 1.1% increase in the odds of the selected outcome, after adjusting for other factors.
Includes dentists, psychologists, nursing students, and medical students.
For each diagnosis, the AOR identifies the increase or decrease in the likelihood of the selected outcome based on a reference factor.
Includes all other diagnoses in the dataset (approximately 250 diagnoses).
Discussion
With nearly 5 billion passengers traveling by air over the past year,1 the commercial airspace represents a suspended metropolis, with around 1.5 million people in the sky at any given moment. Considering the sheer volume of air travelers, in-flight medical events may occur simply by chance, as medical issues that would otherwise arise on land instead unfold during a flight. The growing trend of medical tourism may further contribute to in-flight medical events, as some passengers board flights soon after medical procedures or while experiencing complex health conditions.16 Additionally, the unique physiologic stressors of air travel (eg, restricted mobility, reduced cabin pressure, and relative hypoxia) can exacerbate pre-existing conditions, precipitate acute medical events, or lead to injuries from turbulence and other in-flight hazards.17,18,19 Consequently, in-flight medical events are an unavoidable aspect of air travel, requiring structured response systems and proactive preparedness to ensure passenger safety.2,3,7
Leveraging a large multinational dataset, we characterized the epidemiology, management, and short-term outcomes of in-flight medical events, identifying key factors associated with aircraft diversion and postflight medical care. Neurological and cardiovascular conditions were the leading causes of aircraft diversion, with stroke, altered mental status, and acute cardiac emergencies carrying the highest odds of necessitating an unscheduled landing.
Our findings build on previous in-flight medical events studies2,3,4,5,6,7,9,10,12,13,14,19,20,21,22 while expanding the scope to a larger, more diverse global airline network of 84 airlines, including 17 US-based carriers. Similar to previous research, we found that most in-flight medical events were managed conservatively, requiring only in-flight advice.5,10,11 Interestingly, our study reports a lower diversion rate (1.7%) compared with prior reports (range, 4%-15%),2,10,19,23 but in line with more contemporary figures,5,24 possibly reflecting advancements in telemedicine and improved airline medical protocols. However, it is more likely that this finding might be related to a more liberal use of ground-based medical support centers in the current era, with a lower threshold for calls once reserved for only the most consequential cases. This shift is further supported by our finding of a higher incidence of in-flight medical events (39 events per 1 million passengers and 1 event per 212 flights) compared with the 16 in-flight medical events per 1 million passengers and 1 event per 604 flights rates reported by Peterson et al.10 Even within our sample, the incidence of in-flight medical events varied significantly among airlines, ranging from 7 to 257 events per 1 million passengers, suggesting differing thresholds for ground-based medical support involvement across carriers worldwide. To account for differences in exposure relative to flight duration, we also reported the incidence of in-flight medical events per billion RPKs, a standard aviation metric that more accurately reflects time at risk compared with enplanement-based rates. For this reason, we believe that incidence per billion RPKs should be the standard metric for epidemiologic reporting of in-flight medical events.
Medical volunteers played an essential role in in-flight medical events, assisting in 32.7% of cases. Physicians were the most frequently involved, providing care in nearly two-thirds of cases where a medical volunteer assisted (or 20.1% of all in-flight medical events), and their involvement was significantly associated with increased odds of diversion. However, our data establish only an association, not causation, making it unclear whether medical volunteer involvement contributed to more diversions or reflected the greater complexity of these events. The observed association between medical involvement and aircraft diversion likely reflects confounding by indication, as physicians are more often called upon during higher-acuity events. This variable is also limited by the uncertainty regarding physician passenger presence across flights. Despite concerns about liability, protections such as the Aviation Medical Assistance Act in the US provide legal safeguards for volunteer responders.25 However, global variations in Good Samaritan protections and duty-to-respond laws should be considered, as these regulations differ between jurisdictions.26 In the US, Canada, England, and Singapore, medical volunteers are not legally obligated to provide assistance,8,27,28,29 whereas in many European countries and Australia, physicians are required to intervene when called on during an emergency.8,26,29 These differences in legal mandates may influence the willingness of medical professionals to respond to in-flight medical events, particularly when the presenting condition falls outside their primary area of expertise.30,31
The decision to divert an aircraft goes beyond medical factors; it involves complex operational considerations and ultimately rests with the captain. While certain conditions, such as stroke, acute cardiac events, and altered mental status, are strongly associated with diversion, other logistical factors also play a role in flight crew decisions. Weather conditions, fuel load, proximity to appropriate medical diversion points or original destination, and the ability to stabilize the patient in-flight all contribute to the final determination.2,32 Moreover, diversions may not always be feasible, even in life-threatening emergencies. This is especially true for aircraft on transoceanic or transpolar routes, or those flying over remote or inhospitable regions, where immediate landing is not an option. In such scenarios, medical management must focus on stabilizing the passenger until the aircraft reaches a suitable destination, which may be the originally planned arrival airport. Diversions are costly and disruptive for all involved.2,32 However, despite the logistical and operational challenges, most diversion decisions are made on a medical basis and are not contested by airlines in real time.
Unsurprisingly, the majority of in-flight medical events occurred on long-haul or ultralong-haul flights, international routes, and wide-body aircraft. This finding aligns with expectations, as longer flight durations and increased passenger capacity raise the probability of a medical event occurring during a flight. Larger aircraft are also more likely to have medical volunteers among the passengers, potentially improving the ability to manage in-flight medical events onboard in collaboration with the ground-based medical support center. Additionally, smaller aircraft used for shorter flights often have more limited air-to-ground communication but greater availability of landing options.
Oxygen therapy was the most frequently administered intervention (40.8% of cases); this was not unexpected considering flight crew are trained to apply supplemental oxygen to passengers experiencing distress, even before seeking medical advice. The widespread use of oxygen therapy underscores both the physiologic challenges associated with air travel and the established training standards of flight attendants. Commercial aircraft typically cruise at altitudes of 32 000 to 43 000 feet, maintaining a cabin pressure equivalent to 6000 to 8000 feet above sea level.17,33 This results in an alveolar partial pressure of oxygen of approximately 72 to 64 mm Hg compared with a partial pressure of oxygen of approximately 100 mm Hg at sea level, which may contribute to hypoxemia, particularly in passengers with preexisting cardiopulmonary conditions.17,33 The well-documented decrease in oxygen saturation during commercial flights may explain why supplemental oxygen was administered in nearly half of in-flight medical events, as even otherwise healthy individuals can experience transient hypoxemia at altitude.17,33 These physiologic effects of flight underscore the importance of ensuring oxygen availability onboard, particularly for passengers with chronic respiratory disease or other medical conditions that predispose them to hypoxemia. Notably, the oxygen routinely available on commercial aircraft is not primarily intended for medical use but rather for flight attendants during depressurization emergencies. Passengers at high risk of hypoxemia due to underlying conditions should travel with an approved oxygen concentrator, even if they do not require supplemental oxygen at sea level.
Strengths and Limitations
This study has several strengths, including its large sample size, robust structured dataset, and global scope. It also has important limitations. First, as a retrospective analysis of contemporaneously generated clinical encounters, our findings are inherently subject to potential data entry errors. However, this was mitigated by multiple cross-referencing and validation procedures to ensure accuracy. Second, we could not assess patient trajectories beyond immediate postflight disposition, limiting insight beyond short-term outcomes. Third, we were unable to account for the precise timing of the medical event relative to the remaining flight duration, which may influence the likelihood of diversion, particularly when an event occurs during final descent. Lastly, our analysis was limited to in-flight medical events reported to the ground-based medical support center. Center involvement varies considerably, as evidenced by the 4-fold difference in reported in-flight medical events among US-based airlines in our subcohort. This variation is likely driven by airline-specific protocols governing when ground-based medical support consultation is sought, rather than random chance.
Conclusions
In this cohort study of 77 790 in-flight medical events, we found that such events occur more frequently than previously reported. With the continued expansion of global commercial air travel, in-flight medical events will remain an inevitable challenge, requiring coordinated responses and well-defined medical protocols. Precise understanding of these events is critical to inform airline policies, optimize flight crew training, and enhance in-flight medical preparedness.
eTable 1. In-Flight Medical Events According to Diagnosis Category and Outcome Results of quality assessment per study
eTable 2. In-Flight Medical Events According to Diagnostic Impression and Outcome
Data Sharing Statement
References
- 1.Global outlook for air transport: a world with lower oil prices? International Air Transport Association. December 2024. Accessed April 17, 2025. https://www.iata.org/en/iata-repository/publications/economic-reports/global-outlook-for-air-transport-december-2024/
- 2.Martin-Gill C, Doyle TJ, Yealy DM. In-flight medical emergencies: a review. JAMA. 2018;320(24):2580-2590. doi: 10.1001/jama.2018.19842 [DOI] [PubMed] [Google Scholar]
- 3.Nable JV, Tupe CL, Gehle BD, Brady WJ. In-flight medical emergencies during commercial travel. N Engl J Med. 2015;373(10):939-945. doi: 10.1056/NEJMra1409213 [DOI] [PubMed] [Google Scholar]
- 4.Baltsezak S. Clinic in the air? a retrospective study of medical emergency calls from a major international airline. J Travel Med. 2008;15(6):391-394. doi: 10.1111/j.1708-8305.2008.00233.x [DOI] [PubMed] [Google Scholar]
- 5.Ceyhan MA, Menekşe IE. In-flight medical emergencies during commercial travel. J Travel Med. 2021;28(7):1-8. doi: 10.1093/jtm/taab094 [DOI] [PubMed] [Google Scholar]
- 6.Cummins RO, Schubach JA. Frequency and types of medical emergencies among commercial air travelers. JAMA. 1989;261(9):1295-1299. doi: 10.1001/jama.1989.03420090059031 [DOI] [PubMed] [Google Scholar]
- 7.Graf J, Stüben U, Pump S. In-flight medical emergencies. Dtsch Arztebl Int. 2012;109(37):591-601. doi: 10.3238/arztebl.2012.059 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Hédouin V, Lallemand M, Révuelta E, Dreszer MA, Gosset D. Medical responsibility and air transport. Med Law. 1998;17(4):503-506. [PubMed] [Google Scholar]
- 9.Jagoda A, Pietrzak M. Medical emergencies in commercial air travel. Emerg Med Clin North Am. 1997;15(1):251-260. doi: 10.1016/S0733-8627(05)70294-7 [DOI] [PubMed] [Google Scholar]
- 10.Peterson DC, Martin-Gill C, Guyette FX, et al. Outcomes of medical emergencies on commercial airline flights. N Engl J Med. 2013;368(22):2075-2083. doi: 10.1056/NEJMoa1212052 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.Rotta AT, Alves PM, Nerwich N, Shein SL. Characterization of in-flight medical events involving children on commercial airline flights. Ann Emerg Med. 2020;75(1):66-74. doi: 10.1016/j.annemergmed.2019.06.004 [DOI] [PubMed] [Google Scholar]
- 12.Sand M, Bechara FG, Sand D, Mann B. Surgical and medical emergencies on board European aircraft: a retrospective study of 10189 cases. Crit Care. 2009;13(1):R3. doi: 10.1186/cc7690 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13.Shi R, Jiang W, Yang J, et al. Characteristics of in-flight medical emergencies on a commercial airline in mainland China: retrospective study. JMIR Public Health Surveill. 2024;10:e63557. doi: 10.2196/63557 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Szmajer M, Rodriguez P, Sauval P, Charetteur MP, Derossi A, Carli P. Medical assistance during commercial airline flights: analysis of 11 years experience of the Paris Emergency Medical Service (SAMU) between 1989 and 1999. Resuscitation. 2001;50(2):147-151. doi: 10.1016/S0300-9572(01)00347-1 [DOI] [PubMed] [Google Scholar]
- 15.United States Department of Transportation. Bureau of Transportation Statistics. Accessed March 11, 2025. https://www.transtats.bts.gov/
- 16.Potin M, Carron PN, Genton B. Injuries and medical emergencies among international travellers. J Travel Med. 2024;31(1):1-13. doi: 10.1093/jtm/taad088 [DOI] [PubMed] [Google Scholar]
- 17.Humphreys S, Deyermond R, Bali I, Stevenson M, Fee JPH. The effect of high altitude commercial air travel on oxygen saturation. Anaesthesia. 2005;60(5):458-460. doi: 10.1111/j.1365-2044.2005.04124.x [DOI] [PubMed] [Google Scholar]
- 18.Scurr JH, Machin SJ, Bailey-King S, Mackie IJ, McDonald S, Smith PD. Frequency and prevention of symptomless deep-vein thrombosis in long-haul flights: a randomised trial. Lancet. 2001;357(9267):1485-1489. doi: 10.1016/S0140-6736(00)04645-6 [DOI] [PubMed] [Google Scholar]
- 19.Alves PM, Nerwich N, Rotta AT. In-flight injuries involving children on commercial airline flights. Pediatr Emerg Care. 2019;35(10):687-691. doi: 10.1097/PEC.0000000000000993 [DOI] [PubMed] [Google Scholar]
- 20.Cummins RO, Chapman PJ, Chamberlain DA, Schubach JA, Litwin PE. In-flight deaths during commercial air travel. How big is the problem? JAMA. 1988;259(13):1983-1988. doi: 10.1001/jama.1988.03720130047028 [DOI] [PubMed] [Google Scholar]
- 21.Silverman D, Gendreau M. Medical issues associated with commercial flights. Lancet. 2009;373(9680):2067-2077. doi: 10.1016/S0140-6736(09)60209-9 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22.Speizer C, Rennie CJ III, Breton H. Prevalence of in-flight medical emergencies on commercial airlines. Ann Emerg Med. 1989;18(1):26-29. doi: 10.1016/S0196-0644(89)80306-3 [DOI] [PubMed] [Google Scholar]
- 23.Sirven JI, Claypool DW, Sahs KL, et al. Is there a neurologist on this flight? Neurology. 2002;58(12):1739-1744. doi: 10.1212/WNL.58.12.1739 [DOI] [PubMed] [Google Scholar]
- 24.Kim JH, Choi-Kwon S, Park YH. Comparison of inflight first aid performed by cabin crew members and medical volunteers. J Travel Med. 2017;24(2):1-6. doi: 10.1093/jtm/taw091 [DOI] [PubMed] [Google Scholar]
- 25.Aviation Medical Assistance Act of 1998, Pub L. No. 105-170. (1998). Accessed August 17, 2025. https://www.congress.gov/bill/105th-congress/house-bill/2843/text
- 26.Newson-Smith MS. Passenger doctors in civil airliners: obligations, duties and standards of care. Aviat Space Environ Med. 1997;68(12):1134-1138. [PubMed] [Google Scholar]
- 27.de Caprariis PJ, Di Maio A. Medical legal implications when providing emergency care on a commercial flight. Aerosp Med Hum Perform. 2021;92(7):588-592. doi: 10.3357/AMHP.5760.2021 [DOI] [PubMed] [Google Scholar]
- 28.Shepherd B, Macpherson D, Edwards CM. In-flight emergencies: playing the good Samaritan. J R Soc Med. 2006;99(12):628-631. doi: 10.1177/014107680609901211 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 29.Wong M. Doctor in the sky: medico-legal issues during in-flight emergencies. Med Law Int. 2017;17(1-2):65-98. doi: 10.1177/0968533217705693 [DOI] [Google Scholar]
- 30.Hawati SM, Binobaid F, Alsaeigh A, et al. Assessing emergency medicine, family medicine, and ICU doctors’ knowledge, confidence, and attitude in managing in-flight medical emergencies in the Kingdom of Saudi Arabia hospitals: a cross-sectional study. Cureus. 2025;17(2):e78359. doi: 10.7759/cureus.78359 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 31.Chatfield E, Bond WF, McCay B, et al. Cross-sectional survey of physicians on providing volunteer care for in-flight medical events. Aerosp Med Hum Perform. 2017;88(9):876-879. doi: 10.3357/AMHP.4865.2017 [DOI] [PubMed] [Google Scholar]
- 32.Lewis BA, Gawron VJ, Esmaeilzadeh E, et al. Data-driven estimation of the impact of diversions due to in-flight medical emergencies on flight delay and aircraft operating costs. Aerosp Med Hum Perform. 2021;92(2):99-105. doi: 10.3357/AMHP.5720.2021 [DOI] [PubMed] [Google Scholar]
- 33.Cottrell JJ, Lebovitz BL, Fennell RG, Kohn GM. Inflight arterial saturation: continuous monitoring by pulse oximetry. Aviat Space Environ Med. 1995;66(2):126-130. [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
eTable 1. In-Flight Medical Events According to Diagnosis Category and Outcome Results of quality assessment per study
eTable 2. In-Flight Medical Events According to Diagnostic Impression and Outcome
Data Sharing Statement
