Ryanair pilots based in the U.K. have authorized a series of summer strikes in a dispute with the budget carrier over pay and benefits.

Members of the British Airline Pilots Association voted by a ratio of 4-to-1 in favor of the strikes set for Aug. 22-23 and Sept. 2-4.

The union says the dispute involves pensions, loss of license insurance, maternity benefits, allowances, and pay.

Brian Strutton, the union's general secretary, said Wednesday that pilots don't want to disrupt passengers' travel plans, but "at the moment it seems we have no choice" because Ryanair hasn't made a formal offer to resolve the dispute.

A Ryanair spokesman says many of the airline's pilots aren't members of the union and that union members "have no mandate to disrupt our customers' holidays and flights."

Ryanair boss Michael O’Leary has told staff to prepare for as many as 900 job cuts as he warned that the Irish budget airline’s expansion plans would be slowed dramatically following the grounding of the Boeing 737 Max.

O’Leary said in a video message to employees that Ryanair had an excess of more than 500 pilots and about 400 cabin crew. On top of that, he said, the airline would need 600 fewer people in those roles next summer than it had planned for before the worldwide grounding of the Max aircraft following two fatal crashes, the Guardian reports.