Table 4.

Notes for Fig. 1, containing full names of top 20 airports.

IATA-Code	Airport
ATL	Hartsfield–Jackson Atlanta International Airport
CAN	Guangzhou Baiyun International Airport
CKG	Chongqing Jiangbei International Airport
CLT	Charlotte Douglas International Airport
DEL	Indira Gandhi International Airport
DEN	Denver International Airport
DFW	Dallas Fort Worth International Airport
HND	Tokyo International Airport
IAH	George Bush Intercontinental Airport
KMG	Kunming Wujiaba International Airport
LAX	Los Angeles International Airport
MEX	Mexico City Airport
MIA	Miami International Airport
ORD	Chicago O’Hare International Airport
PEK	Beijing Capital Airport
PHX	Phoenix Sky Harbor Airport
SEA	Seattle SEATAC Airport
SHA	Shanghai Hongqiao Airport
SZX	Shenzhen Bao’an International Airport
XIY	Xian Airport