An Australian Jetstar flight from Sydney to Cairns has been forced to divert to Brisbane about 40 minutes into its trip after filling with smoke.
Video shot by a passenger showed smoke in the cabinet as staff prepared to get passengers off the aircraft on landing.
Jetstar said there had been a technical fault with an engine.
The budget airline denied it was an emergency landing and said smoke entered the cabin only after the plane landed.
But some passengers reported hearing a noise and smoke filling the cabin while the plane was still in the air.
Passenger Nick Trompf told the Courier Mail it had been "pretty scary",
"Just as we flew over Narrabri smoke started to fill the cabin and there was a scraping and grating noise."
Flight JQ956 was on its way from Sydney to Cairns when the captain shut down one of the aircraft's engines and diverted to Brisbane "as a precaution" the budget airline said.
"The smoke would have entered the cabin through the air conditioning unit, which runs via air from the engines," it said in a statement, adding that it was investigating the cause.
Passengers were transferred to another flight to Cairns later on Thursday evening. There were no reports of injuries.