A union representing Lufthansa's pilots says they will walk off the job at Frankfurt airport for eight hours on Tuesday, preventing departures by Germany's biggest airline from its busiest airport.

The Vereinigung Cockpit union said Monday that pilots on international long-distance flights from Frankfurt will walk out from 9 a.m. to 5 p.m. (0700 to 1500 GMT). The work stoppage follows several strikes in the past three weeks by Lufthansa pilots in Munich and pilots at Lufthansa's Germanwings subsidiary.

The two sides are locked in a dispute over the pilots' demand that Lufthansa keep paying a transition payment for those wanting to retire early. The airline, which faces tough competition from European budget airlines and major Gulf airlines, wants to cut those payments.