The co-pilot who was charged of deliberately crashing Germanwings A320 flight on Tuesday had passed all the flight and medical tests and was "100 percent fit to fly", said Lufthansa chief executive Carsten Spohr on Thursday.

He told reporters in a press conference in Cologne that Lufthansa and its low-cost subsidiary Germanwings was "speechless" that the flight 4U9525 was deliberately crashed by its co-pilot.

He said the co-pilot, identified by French prosecutor earlier on Thursday as 28-year-old Andreas Lubitz, started his training in an aviation school in Bremen, Germany, in 2008, but interrupted for a while for reasons Spohr didn't mention.

The training then resumed, said Spohr, and he started to work as a co-pilot for Germanwings since 2013.

According to Spohr, a pilot candidate for Lufthansa and Germanwings must receive a fitness test after training interruption for whatever reasons and can only continue if the fitness was established.

The co-pilot of AU9525 passed all flights and medical tests and was "100 percent fit to fly with no restriction", Spohr said.

According to Spohr, there are regular aeronautical examinations and once a year a medical check after pilot finished training in an aviation school. But "there is no regular psychological checks, " said Spohr.

He also noted that the event is "an incredibly tragic individual case", adding that the company has "firm confidence" in the selecting and training procedure as well as the work of its pilots.

"No matter what security measures are invested in the company, such individual cases can not be ruled out," said Spohr in Cologne.

Spohr also said that there is no indication that one would suspect co-pilot's terrorist intentions, "We can only speculate on the motives".