Qantas plane returns to Bangkok after 'bang'

A Sydney-bound Qantas flight was forced to turn back to Bangkok with engine problems after a bang onboard the plane, the airline says.

The Boeing 747 turned back one hour into the Bangkok-Sydney Q52 flight about 9.30pm (AEDT) on Sunday after there was a bang and the plane vibrated, a Qantas spokesman told AAP.

"About one hour after take-off, there was a bang and some vibrations were felt through the aircraft," he said.

The pilot turned off one of the four engines as a safety precaution and the plane, carrying 356 passengers, landed safely back at Bangkok airport at 10.47pm (AEDT).

No emergency landing was required and all passengers were being accommodated on other services, the spokesman said.

One passenger reported seeing sparks shooting out of the engine, Macquarie Radio reported.

"There was some white sparks shooting out of the engine and then they informed us of what was going on, that the engine had been shut down and we were returning to Bangkok," a passenger known only as David said.

It comes as an estimated 60,000 Qantas passengers have been affected by a series of rolling strikes by engineers and ground crews.

The airline last week cancelled 400 domestic flights over the next month, blaming the disruptions on engineers' strikes.

-AAP