Passengers could see delays or cancellations at Ryanair base airports in Spain which are Madrid, Barcelona, Girona, Malaga, Seville, Valencia, Alicante, Santiago de Compostela, Palma de Mallorca and Ibiza.
According to data from USO, the union running the strike, more than 200 Ryanair flights were delayed on Wednesday.
Around 11 flights were cancelled, although these were primarily domestic flights operating from Barcelona.
Ryanair claimed that only one percent of its scheduled flights were affected by the strikes.
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The airline said “the vast majority of Ryanair crews are working as normal” and added it expected “minimal disruption to its flights”.
Despite the striking crew, some Ryanair flights will still operate due to a Spanish law protecting the right of people to travel.
This means the cabin crew will still have to run the flight and perform the safety briefing but may not serve passengers refreshments or provide extra services.
Ryanair crew in Spain have more action planned for tomorrow and between July 18-21 and July 25-28.
easyJet cabin crew will strike on July 15 in industrial action that is set to continue over the weekend.
easyJet has three bases in Spain which are Malaga, Barcelona and Palma de Mallorca.
The budget airline said: “Should the industrial action go ahead, there could be some disruption to our flying programme to and from Malaga, Palma and Barcelona during the strike period but at this stage, easyJet plans to operate its full schedule and we would like to reassure customers that we will do everything possible to minimise any disruption.”
The USO union has criticised the airline for offering Spanish workers a lower salary than other workers in Europe.
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It claimed: “The conclusion is very clear, at easyJet there is money for everything, except for Spain.”
The strikes come as tourist officials in Spain’s Costa del Sol panic over a warning from the UK Government.
A travel warning was issued by the Foreign Office for British tourists over the strikes which said: “Planned strike action in July may cause some disruption to easyJet and Ryanair flights to and from Spain.”
The tourism sector in the Costa del Sol has said that this type of warning is not common when it comes to industrial action.
Officials are concerned that the warning could put British tourists off travelling to Spain for holidays.
Passengers with a cancelled flight are entitled to another flight on their intended day of travel if one is available.
This is the case even if the only available flight is on a rival airline or in a more expensive seat.
If a flight is cancelled last minute, passengers could be entitled to cash compensation if it is the airline’s fault.