Passengers had to evacuate an American Airlines aircraft at Heathrow on emergency slides.
Smoke was found in the cabin of the London to Charlotte flight at Terminal 3 on Sunday morning. There were 277 passengers and 12 crew on board.
About 25 passengers used the slides but there were “no significant injuries”.
A passenger on a flight from Helsinki, Ross Hiscock, said he saw “smoke coming from the tail-end of the plane” parked next to his and saw passengers escape.
American Airlines Flight 731 was subsequently cancelled and alternative arrangements are being made, the airlines said.
A Heathrow spokeswoman said a “technical issue” was identified and the problem was resolved, the BBC reported.
American Airlines said: “American Airlines Flight 731 London-Heathrow to Charlotte experienced smoke in the cabin while still on the ground in LHR.
“Three slides were deployed on the aircraft and approximately 25 passengers deplaned via the slides.
“The rest of the passengers and crew safely deplaned via the jet bridge.
“A small number of the passengers and crew are being seen by medical personnel but no significant injuries have been reported.”