The unions include those representing pilots in two of Ryanair's biggest markets, a union source told Reuters, declining to name which markets they were.

The temporary suspension is a reaction to Ryanair's closure of bases in the Dutch city of Eindhoven and Bremen in Germany and the reduction of capacity in the German region of Niederrhein. The European Cockpit Association in October described the move as a "declaration of war".

Ryanair has also threatened to close two bases in the Canary Islands if cabin crew in Spain do not sign up to a collective labor agreement by next week, the ECA said on Wednesday.

Spanish cabin crew called off planned strikes last week after reaching a preliminary agreement on contracts.

A spokesman for Ryanair was not available for immediate comment.

Europe's largest low-cost carrier suffered a number of strikes last year by pilots and cabin crew, grounding hundreds of flights across Europe, after it agreed to recognize unions for the first time in 2017 following rostering difficulties.

But it got through Christmas without any industrial action, having made progress with a number of unions that it expects to translate into agreements with its major unions by the end of March.

(Reporting by Conor Humphries, writing by Padraic Halpin; editing by Jason Neely)