The British Airline Pilots Association (BALPA) has voted for two pilot walkouts, one from August 22-23, and one from September 2-4.
The association denied wanting to ruin travel plans, but said that Ryanair had “refused” to “deal with unions” for decades.
Union bosses claimed 79.5% support for the strike action, but Ryanair said that fewer than 50% of its UK pilots were members of BALPA, and said that just 57% of these had voted, bringing the total support for the strike to less than 30%.
The dispute centres on pay, at a time when Ryanair reported has already reported profit drops and potential job losses. Grievances also concern issues such as pensions, maternity benefits, and licence insurance.
Yet, the airline claims that its UK pilots were granted a 20% pay rise last year.
Brian Sutton, general secretary of BALPA, said: “No pilot wants to spoil the public's travel plans but at the moment it seems we have no choice. We have had no formal offer from Ryanair and it is imperative that we resolve this dispute urgently to avoid strike action.”
A further statement said: “We have made no progress with Ryanair management on any of those areas at all, seemingly because Ryanair management cannot understand how to go about working with us constructively, or how to negotiate.”
A Ryanair spokesperson said: “BALPA have no mandate to disrupt our customers’ holidays and flights, particularly at a time when UK pilots are facing job losses due to the Boeing Max delivery delays, and the threat of a no-deal Brexit.”
Ryanair serves 33 airports in France, including Paris-Beauvais, Bordeaux, Brest, Grenoble, Lille, Lyon, Nantes, Perpignan, Rodez and Saint-Etienne.
While most of the two million passengers expected to fly on the strike days are unlikely to be affected - as they will not be on aircraft flown by UK pilots - some flights within Europe on strike days could be delayed or cancelled due to knock-on effects.
Up to one-third to one-half of UK-piloted flights may be cancelled. Flights to and from the UK, including connections, are likely to be worst-affected.
Ryanair flights within Europe regularly use pilots based in France, Spain, Italy and elsewhere - who would not be affected by these strikes - but Irish pilots are also expected to announce strike action this week, and Ryanair cabin crew in Portugal are set to walk out for five days from August 21.
Flights the day before or the day after strike days are unlikely to be badly affected.
Passengers with booked tickets will only find out if their flights have been cancelled two or three days ahead.
Refunds, alternative travel arrangements and expenses incurred in case of delay will only be available once Ryanair has formally cancelled the flights. Passengers who cancel their tickets themselves before the flight will not be eligible for refunds.
It is not yet clear whether Ryanair will be forced to pay compensation for cancelled flights. Civil Aviation Authority rules state that compensation of €250 is due for passengers of cancelled flights up to 1,500km, but Ryanair claims that the strike is “beyond its control” so the rules do not apply.
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