BERLIN, March 24 -- Lufthansa, the parent company of budget airline Germanwings, confirmed Tuesday night that the Airbus A320 which crashed in southern France was in "Aircraft on ground" (AOG) mode on Monday.

A spokeswoman of the airline told Xinhua in telephone that the plane had a technical problem with its nose landing door and was prevented from flying in Germany's Duesseldorf airport on Monday.

She thus confirmed a previous report from German Der Spiegel magazine that the plane was in AOG mode one day before it crashed in southern French Alps with 150 people, including two babies and 16 German students, on board.

The problem was then "completely solved", and left "no security risks", stressed the spokeswoman, adding that the plane returned to normal operation on Monday morning.

She declined to confirm another report that several pilots at Germanwings refused to fly planes with the same model as the crashed A320 aircraft, only saying that some pilots could not take up their position due to "personal reasons" which her company could understand.

Earlier on Tuesday, Germanwings chief executive Thomas Winkelmann told reporters that the crashed plane received its last "routine check" on Monday in Duesseldorf by Lufthansa Technik.

The plane left Spain's Barcelona Tuesday morning for Duesseldorf airport. It started to descent shortly after reaching its cruising altitude of 38,000 feet and crashed in a snow covered area in southern French Alps where it is particularly difficult to access and only helicopters could reach.

Causes of the crash remained unclear. German Federal Bureau of Aircraft Accident Investigation (BFU) has sent investigators to France and a joint investigation by France, Germany and Spain is opened to find out the causes of the tragedy. A group of experts from Lufthansa, Germanwings and Airbus were also dispatched later on Tuesday to the crash site.