Berlin - A pilots' union in Germany called a sudden strike Tuesday to disrupt the air-passenger operations of two Lufthansa domestic subsidiaries and back up demands for a big hike in pay.

There was only two hours of warning that many flights by the Eurowings and CityLine units of Lufthansa, which operate short-haul connections within Germany and to nearby nations, would be grounded for 36 hours from noon till midnight Wednesday.

The union, Vereinigung Cockpit, represents pilots and flight-deck engineers. Some flights were expected to continue, since the union does not represent all the pilots employed at the two lines.

Two weeks ago the union held a 24-hour strike that knocked out 600 flights and caused many others to take off hours late. The union has about 1,000 members working for the two airlines, which pay flight crew less than the parent company Lufthansa does.

The union said take-offs from Frankfurt, Dusseldorf, Hanover, Stuttgart, Berlin-Tegel, Leipzig and Hamburg would be especially affected. Lufthansa appealed to passengers to ring its booking centres and shift travel to other days.

Lufthansa spokesman Michael Lamberty said the airlines would also issue vouchers so passengers could use other airlines or express trains at no extra charge.

Eurowings and Cityline fly propeller planes and small jetliners to and from many provincial airports.

The union is demanding pay scales closer to those used at Lufthansa, but has not publicized the extent of its demands. (dpa)