BERLIN (Reuters) - German passenger rights company Flightright is taking Ryanair RYA.I to court over whether it should pay financial compensation to passengers affected by strikes at Europe's largest low-cost carrier.

An aircraft of low-cost airliner Ryanair is seen behind a fence while being parked at the tarmac of Weeze airport near the German-Dutch border during a wider European strike of Ryanair airline crews to protest slow progress in negotiating a collective labour agreement at Weeze airport, Germany August 10, 2018. REUTERS/Wolfgang Rattay

Ryanair had to cancel around 1 in 6 flights on Friday due to a walk-out by pilots in five European countries, disrupting an estimated 55,000 travelers.

The worst affected country was Germany, where 250 flights were canceled, affecting around 42,000 passengers.

EU rules state that passengers can claim monetary compensation of up to 400 euros for flights within the region for canceled or delayed flights, unless the reason is extraordinary circumstances, such as bad weather.

Strikes have generally fallen under extraordinary circumstances although a ruling by the European Court of Justice in April said that a wildcat strike by staff at German airline TUIfly following a restructuring could not be classed as extraordinary circumstances.

Flightright said it believes Ryanair is therefore obliged to pay monetary compensation to customers and so has filed a complaint with a court in Frankfurt in a bid to clarify the rules around strikes.

A spokeswoman for the court said she was aware of the Flightright statement, but that she had not yet seen the complaint.

Ryanair said it fully complies with the European legislation on the matter, known as EU261.

“Under EU261 legislation, no compensation is payable when the union is acting unreasonably and totally beyond the airline’s control. If this was within our control, there would be no cancellations,” a spokesman said.

Passenger rights groups such as Flightright help passengers to claim compensation from airlines under EU261 rules but in exchange for a share of the compensation received.

Many European airlines, including Ryanair, therefore urge passengers to file claims with them directly instead.

(This version of the story corrects paragraph 2 to read “on Friday” instead of “last week”)