A Jeju Air plane that crashed in December during an emergency landing after a bird strike could have kept flying on the damaged engine that was still working after pilots shut down the other one, according to an update from South Korean investigators.

The Boeing 737-800 instead belly-landed at Muan airport without its landing gear down, overshot the runway and erupted into a fireball after slamming into an embankment, killing all but two of the 181 people on board.

Investigators have not yet produced a final report into the deadliest air disaster on South Korean soil, but information about the plane's two engines has begun to emerge.