(AP Photo/Michael Probst)

FRANKFURT - A strike at Frankfurt airport led to the cancellation of about 20 per cent of its flights Monday.

The strike by 200 members of the GdF union strike was to continue at least until 5 a.m. Wednesday.

Most of the cancellations were flights operated by Lufthansa within Europe.

Airport operator Fraport AG said in a statement that slightly longer waiting times can be expected in the terminals but that operations otherwise "continue to run smoothly."

Lufthansa is listing cancelled flights on its website and notifying customers by text message.

Lufthansa said it called off about 100 round trips, or 200 flights, on Monday and expected that number to fall to 80 round trips on Tuesday. Passengers are being offered refunds or the opportunity to rebook free of charge for flights cancelled by the strike, the airline said.

Fraport labour relations head Herbert Mai said the airport managed to have 80 per cent of flights operate Monday, "which means we are getting better every day."

He said the cancellations were "a hardship for a lot of passengers and clients of Frankfurt Airport" and that management "repeatedly let the GDF know that we are prepared to talk."

The GdF union, which also represents ground workers, has been locked in a pay dispute with Fraport AG for months. The strike came after the company rejected the result of an arbitration panel as excessive, saying it would inappropriately inflate pay scales for the other airport workers.