After applying online , and presumably meeting the minimum requirements , you will receive an email asking you to agree to releasing your personal information to DLR Hamberg via the aero recruiting site.
DLR is the German equivalent of NASA, and conducts "fearsome " physiological tests for the DLR and/or third parties.
After Germanwings, i guess they are a bit over cautious.
I do get the impression that fluent German language skills are highly desirable , although not mentioned in basic job requirements.