Ryanair's efforts to avert its first ever pilots strike collapsed on Friday as pilots in Germany held a four-hour walkout although airports said there had been little impact on flights.

The Irish budget carrier had sought to avert a series of threatened strikes across Europe over Christmas last week by giving up its long-held opposition to recognising unions.

However, Germany's Vereinigung Cockpit (VC) union said it would stage a brief walkout as it did not believe Ryanair was serious about recognising unions or sincere in talks.

"This was a warning shot and we started small. However, there is potential for much more," union spokesman Markus Wahl said, ruling out further strikes until after Dec 26.

The strike ran from 4 GMT to 8 GMT when only 16 flights were scheduled.

"All in all there are no significant effects," a spokesman for Berlin airports said, noting that five of seven flights had departed, with one delayed.

Cologne/Bonn airport said two of three scheduled flights had taken off and the third was delayed. Frankfurt airport said four of six scheduled flights had taken off.

Ryanair was not available for immediate comment. Management had urged pilots to work to get passengers home for Christmas.

But the VC union said after a first meeting that it did not believe Ryanair genuinely wanted to recognise unions and said it wanted to send a message that their pilots were serious about industrial action.

VC said Ryanair had refused to accept two members of a delegation that the union nominated to hold talks with management. One of the pilots was a contractor and one a direct employee, but Ryanair has ended both of their contracts, VC said.

"This has shown us that nothing has changed with Ryanair's management style or how it handles workers' rights," VC President Ilja Schulz told reporters on Thursday.

Ryanair pilots mobilised in September after the carrier announced the cancellation of around 20,000 flights, which it blamed on a rostering problem sparked by a change in Irish regulations.