The airline said that by cutting its scheduled flying programme over the next six weeks by less than 2%, it will create additional standby aircraft which will help restore on-time performance to its 90% average.
But the airline have not yet published a full list of the flights to be affected over the next six weeks - and has only confirmed the flights culled for up until Wednesday September 20.
It added it was "essential that Ryanair release a full list of flights that will be affected so that passengers have as much time as possible to make alternate arrangements".
On Monday, the low-priced carrier said over 98% of its customers will be unaffected by the "less than 50 per day" flight cancellations between Thursday and October 31.
Norwegian Air (NWC.OL) said it had hired more than 140 Ryanair pilots this year, although O'Leary said it had lost less than 100 of its 4,200 pilots and had recruited some from its rival, meaning it could fully crew its peak schedule.
All of Ryanair's flights are short or medium-haul, and the vast majority are to destinations within the European Union, meaning that passengers are entitled to some very specific rules on compensation.
As a result of this change, Ryanair marketing officer Kenny Jacobs says the airline had to allocate a load of annual leave to pilots in September and October.
It's not quite as bad as it sounds - the number of flights in actually less than 2% of the company's total daily flights - but that's not comforting if it's your flight.
You can also get a full refund if the flight wasn't cancelled but was delayed for more than five hours and you no longer wish to travel.
"No clue if our flight will be cancelled". There was dismay from many customers last week after Ryanair announced new reduced checked bag fees and increased check-in bag sizes to encourage more customers to check in bags. When we make a mess in Ryanair, we come out with our hands up.
In a statement Friday, Ryanair's head of communications, Robin Kiely, said the airline was being impacted by having to allocate annual leave to pilots and cabin crew over the next six weeks.
Among those cancelled with be one in four flights out of Stansted and one in 13 flights out of Dublin.
Earlier this afternoon, Michael O'Leary stated that the current cancellations of Ryanair flights across Europe was "a mess of our own making" as thousands of people have seen their travel plans thrown into chaos.
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