Britain's aviation regulator is taking legal action against Ryanair over its refusal to compensate passengers for strike action.
The Civil Aviation Authority (CAA) said the low-cost airline has rejected compensation claims and has now ended its agreement with AviationADR - a CAA-approved body for alternative dispute resolution of passenger complaints.
The CAA said it does not believe the strikes are "extraordinary circumstances", as Ryanair has claimed, and are therefore not exempt, meaning its customers should be compensated.
Ryanair's flights were hit by widespread strikes over the summer by the carrier's pilot and cabin crews, while it also suffered amid the industry-wide air traffic control industrial action that saw thousands of flights cancelled across Europe.
The CAA said passengers with an existing claim will now have to wait until the outcome of its enforcement action against the airline.
The watchdog has made repeated calls for Ryanair to compensate passengers affected by staff strikes.
While airlines can refuse to pay out for "extraordinary circumstances", such as bad weather or air traffic controller strikes, they must pay compensation for disruption caused by strikes held by its own employees.
Ryanair warned over profits in October after it was stung by strike action, combined with higher oil prices.
Ryanair has seen the strike action knock passenger confidence in the company, revealing in October that passengers made fewer forward bookings into the third quarter, including for the October school half-term and Christmas.
Since the summer of severe disruption, Ryanair has been securing a series of agreements with unions across Europe over wages and benefits.
The latest was announced on Tuesday, with German pilots' union VC.