The pilots have planned strikes for seven days between September 18 and 29, the union said.

"Pilots in Ryanair are seeking the same kind of policies and agreements that exist in other airlines -- our demands are not unreasonable," said a statement issued by the British Airline Pilots Association.

They had already refused to work on August 20 and 23, and again this week, but without disrupting the carrier's operations in a major way, the union acknowledged.

Ryanair is facing strike action in several countries, in particular in Spain where a strike has also been called this month to protest the planned closing of some airport bases.

In late July, the airline said it would cut 900 jobs from its total workforce of 13,000.

It blamed delays in delivery of Boeing 737 MAX 200 aircraft that were grounded following two fatal accidents.