Melb plane crash survivors fight for life

A flight instructor and his student are fighting for their lives after their light plane crashed into a Melbourne paddock.

The ultralight Bristell two-seater training plane crashed at Clyde North on Thursday morning, with one person, believed to be a man in his 30s, flown to the Royal Melbourne Hospital in a critical condition.

A second man, thought to be in his 20s, was trapped in the wreckage for more than an hour before being taken to The Alfred Hospital.

He was initially in a serious condition, but that was updated to critical on Thursday afternoon.

Both men remained in critical conditions on Friday morning.

Witness Kane Loveday, who was driving in the area, said "the engine didn't sound anywhere near right".

"It sounded like a lack of power basically and before I could see anything it was below the tree line," he told the Seven Network from the scene.

The light aircraft was registered to Learn to Fly Melbourne, based at Moorabbin Airport.

Civil Aviation Safety Authority spokesman Peter Gibson says the ultralight was on a training flight when it crashed.

"It was on a dual training flight with an instructor and a student on board," Mr Gibson said.

Recreational Aviation Australia will be investigating the crash.