Germanwings is operating 40 flights with aircraft and crews from Air Berlin, Lufthansa and TUIfly today.
The Cologne-based Lufthansa subsidiary has chartered 11 aircraft from other airlines.
Some crew members are unable to work due today as a result of grief and emotional effects from yesterday's crash of a Germanwings Airbus A320 in the French Alps, says the airline. Noting that some employees lost "good friends", it adds that it sympathises with the affected staff.
Germanwings has cancelled a single flight but is otherwise operating its regular schedule today.
Its service from Barcelona to Dusseldorf – the route on which the A320 was lost – has been conducted on schedule by a Germanwings aircraft, albeit under a different flight number and with different routing, online aircraft surveillance data indicates.