Since passengers were alerted of the details of which flight would be affected, pilots have since responded to Ryanair's bonus payments offers for working overtime.
He adds: "We believe these working conditions are leading to pilots leaving the airline after a few years to go work for other airlines".
The Ryanair flight cancellation and pilot shortage fiasco continued Thursday.
O'Leary said the decision was taken to cancel what amounted to 2 percent of the airline's total flights to avoid a sharp increase in delays because of a lack of reserve pilots.
Ryanair has also rejected suggestions that staff are tempted to begin industrial action, saying with captains looking to switch bases and first officers looking for promotions, there's no risk of blue flu. The airline has more "goodies" to propose to pilots, the BBC reports, but O'Leary warned that "if pilots misbehave, that will be the end of the goodies".
He also said there have been no demands for new contracts and told shareholders the blunder had cost the company around £22million and described the situations as a "mess".
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The complaint closely follows Google's refusal to cooperate with the Department of Labour's requests for historical salary data. The former employees claim the company consistently pays men more for doing similar work as women in similar conditions.
Mr O'Leary promised the problem would not recur in 2018 but said there would be a reputational hit from cancelling flights to and from destinations including Barcelona, Brussels, Lisbon, Madrid, Milan and Rome, which would not help future bookings.
The current crisis is being officially blamed on pilot holidays but details have been emerging of an exodus of crews to other budget & low-priced airlines such as Norwegian and Jet2 who operate the same type of aircraft as Ryanair.
The announcement comes just hours after a letter was sent to the company by a group of its existing pilots, rejecting an offer of a tax-free £12,000 bonus in exchange for working overtime.
"There's an underlying problem at Ryanair, which is quite simply that the company can not replace pilots as fast as they quit", he wrote.
O'Leary claimed that this move had not caused the current crisis.
The airline expects to have refunded or processed alternative routes for 95% of affected customers by the end of this week.
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