It has since emerged that the 28-year-old was forced to postpone his pilot training in 2008 because of mental health problems, with a friend saying he was 'in depression.'

Airline bosses confirmed L. had taken several months off work and had to retrain to join the firm, but insisted he was '100% fit to fly' after passing all medical tests.

The revelation will form a central part of the investigation and put pressure on the industry to explain whether enough was done to ensure L. was well enough to pilot a commercial aircraft.