 Commercial operations are remunerated activities which fall within the ICAO definition of CAT . Some are , however , closely aligned to , and considered part of , the GA sector . Public transport operations are non @-@ scheduled , on @-@ demand services flying between points specified by the customer , providing a more flexible service than airline travel . Air taxi operations offer charter services for third parties , and business or corporate aviation uses company @-@ owned aircraft to transport employees and clients . Aircraft used in these operations include business jets , helicopters , and twin piston @-@ engine aeroplanes carrying between six and ten people . An example of this type of operation is the transport by helicopter of spectators to the British Formula One grand <unk> at Silverstone . This involves so many flights that , according to Cranfield Aviation Services , on race day the heliport is temporarily the world 's busiest airport . Aerial work is a small but important component of the commercial GA sector , characterised in its simplest form as remunerated non @-@ transport activities , such as surveying , crop spraying , and emergency services work ( air ambulance and police ) . 
