Pressure grew Wednesday for German airline Lufthansa to explain how Andreas Lubitz - a young man who had exhibited suicidal tendencies and suspended a training programme due to depression - could have been left at the helm of ill-fated Germanwings flight 4U9525, dpa reported. Lufthansa chief executive Carsten Spohr declined to comment Wednesday on when the airline learned of problems plaguing the 27-year-old co-pilot, who is believed to have intentionally crashed the plane into a mountainside in France last week, killing himself and 149 others on board.