Berlin, March 31 (IANS): German investigators of the Germanwings plane crash last week in the French Alps with 150 people on board, are developing a hypothesis that co-pilot Andreas Lubitz crashed the plane in desperation, fearing that he could lose his pilot's licence due to a medical condition.

German daily newspaper Bild reported on Tuesday, citing the statements of one of the case's investigators, that the inquiry currently indicates that this was the "main reason" for the crash, according to Efe news agency.

"The main reason for us right now is that Lubitz was afraid of losing his flying licence because of his poor health," said the investigator, who asked to remain anonymous.

Lubitz would have had to renew his licence in June, according to various reports.

Bild reported that the co-pilot, 27, was admitted at least three times to Dusseldorf University Hospital between February and March of this year.

The German federal prosecutor said on Monday that Lubitz had received psychotherapy years before getting his flying licence for having "suicidal tendencies".

However, Bild also said on Sunday that Lubitz was being treated for a possible retinal detachment.