In the first two weeks of September, punctuality has fallen below 80%, which Ryanair blamed on a number of factors, including air traffic control delays and strikes and weather disruptions.
"We have operated a record schedule and traffic during the peak summer months of July and August but must now allocate annual leave to pilots and cabin crew", spokesman Robin Kiely said on Friday.
Ryanair, an airline popular for its affordable flights, carried more than 100 million passengers a year ago.
So in order to change that, they're, er, just cancelling a load of flights.
The compensation starts at €250 for flights up to 1,500km, €400 for longer European Union flights and €600 for flights outside the European Union longer than 3,500km.
An estimated 270,000 passenger journeys across Europe will be affected by the decision, assuming 40 cancelled flights a day at 90% capacity.
Ryanair apologised for the inconvenience caused to customers by these cancellations.
"Your flight is operating as usual unless you receive an email", the airline said on its website.
However, a Reuters reporter, whose flight from Dublin to Barcelona on 18 September was cancelled on Friday, was offered a choice of a surcharge of €250 to take an earlier flight on the 18th or €60 to take a flight on 19 September.
"Alternatively you must be offered a full refund".
"No one seemed to know why [the flight was cancelled]", he said. Its a bloody disgrace.
"Passengers intending to travel today or over the weekend weren't given any warning to allow them to make alternative arrangements". Norwegian Air Shuttles communications director, Lasse Sandaker-Neilsen told Nettavisen "I can confirm that almost 140 pilots have moved from Ryanair to Norwegian so far this year, both to the new base in Dublin and other bases in Europe".
"The rules say if the airline doesn't have a suitable alternative flight, you have to be booked on a rival airline", he explained, adding that passengers should be able to claim compensation for any cancellations. Compensation may also be payable depending on the notice period Ryanair has given.