Because the plane was flying on automatic pilot, the thrust was reduced according to the faulty reading.

Investigators say the altimeter had given false readings on two previous occasions, but apparently this was not fixed by Turkish Airlines.

On this particular flight, one pilot was receiving training in making a landing by automatic pilot. The investigators say too much time was spent exchanging information between the instructor and the trainee, and not enough was spent checking the actual readings which would have alerted the crew to the problem in time to override the automatic pilot.

Low cloud made it difficult for the crew to assess their actual height.

The aircraft is not designed to be flown using the automatic pilot if the altimeter is not functioning properly, but there is no failsafe system on the aircraft to prevent the automatic pilot from being used when there is a faulty altimeter.

Nine passengers and crew died in the accident, with dozens injured.