Passengers had to be evacuated from part of Gatwick's North Terminal after an empty National Express coach caught fire at a pick-up point outside.
Nobody was hurt in the fire, which took around an half an hour for dozens of firefighters to put out.
A National Express spokesperson told the Daily Telegraph: "An empty National Express vehicle caught fire at Gatwick Airport earlier this afternoon [Friday].
"We are working closely with the emergency services and will continue to assist them.
"We will also carry out our own thorough investigation to establish the cause of this highly unusual incident."
The rail shuttle between the north and south terminals was temporarily suspended. Although part of the terminal was evacuated, flights were not affected by the incident.
A Gatwick Airport spokesman told the Daily Mail: "The fire was on a coach outside the North Terminal building. Some smoke did enter the lower levels of the terminal and we did evacuate people from that area.
"The check-in areas were not affected and the incident did not have an effect on flights."
Sussex Police told the BBC: "Just before 12:30pm on Friday 9 August, emergency services went to the north terminal at Gatwick where a National Express coach had caught fire outside arrivals. The immediate area was cleared and fire was extinguished by 13:00.