The pilots are seeking to increase the pressure on Lufthansa in negotiations over an early retirement scheme. They held a strike at its budget carrier Germanwings at the end of August, followed by a walkout at Frankfurt last week.

The proposed strike at Munich, Lufthansa's biggest airport behind Frankfurt, will run from 0800-1600 GMT, the union said.

While Lufthansa's lucrative long-haul flights were spared from last week's Frankfurt walkout, the union said on Tuesday that this time the strike would affect all flights leaving Munich airport.

Lufthansa said it could not yet say which flights would be affected and described the strike as "incomprehensible".

Lufthansa shares fell after the announcement and were down 1.5 percent at 13.60 euros by 0814 GMT.

Vereinigung Cockpit represents about 5,400 of Lufthansa's around 9,000 pilots and the previous two strikes have cost the airline more than 10 million euros ($12.9 million) in operating profit and have hit bookings.

A three-day pilots' walkout in April wiped 60 million euros from the airline's first-half operating profit.

(Reporting by Victoria Bryan; Editing by David Goodman)