Table 3. Words and bigrams of the 20 topics extracted with LDA from UKAB reports, together with the representative label associated to each topic by FARO’s experts.

Words/Bigrams							Topic
overhead	join	joining	deadside	overhead join	crosswind	circuit	overhead join
student	instructor	student pilot	training	solo	hand	control	training
advised	requested	acknowledged	asked	received	inbound	passed pilot	communication
fast	military	jet	high	fast jet	range	manoeuvres	military jet
survey	manoeuvring	company	operations	conducting	aerobatics	manoeuvres	manoeuvres
runway	go around	go	around	to take off	to land	aircraft established	go around
sectors	sector aircraft	frequency sector	high	coordination	transfer	limit	sector operations
answer	received	finally	decided	they saw	communication	visual contact	communication
site	gliding	winch	glider	launch	active	sites	glider
departure	departing	climb	climbing	airborne	departed	depart	departure
converging	sighting pilot	required give	late sighting	pilot required	considered converging	converging pilot	late sighting
descent	descend	descending	altitude	descended	feet	vertical	descent
trainee	ojti	handover	clearance	instruction	cleared	training	training
helicopter	site	helicopters	helicopter pilot	wing	landing	lifting	helicopter
service	altitude	cloud	weather	receiving	altitude ft	condition	weather
transponder	primary	primary contact	twin	selected	serviceable	equipped	transponder
approach	final	runway	instructed	landing	final approach	leg	final approach
monitor	traffic information	required monitor	warning	definite risk	monitor flight	definite	monitoring
para	drop	parachuting	dropping	parachute	site	para dropping	parachuting
busy	workload	high	working	handover	controlling	inbound	workload
paraglider	paramotor	flypast	paragliders	paraglider pilot	paramotor pilot	paraglider pilots	paraglider
concerned	normal	concerned proximity	standards	pilot concerned	safety standards	pertained	concern
circuit	downwind	visual circuit	leg	pattern	ahead	circuit traffic	downwind leg