Michael O'Leary
Ryanair CEO Michael O'LearyNiklas Halle'n/AFP/Getty Images)

Ryanair boss Michael O'Leary has written to the airline's pilots pledging to offer them better salaries and better working conditions in a bid to convince them to stay.

The letter comes after the Irish carrier was forced to cancel approximately 20,000 flights between September and the end of March, affecting some 700,000 passengers.

The issue stemmed from Ryanair's decision to reschedule its holiday year to run from January to December, rather than the current system, when it runs from April to March. As a result, it had to allocate annual leave to pilots in September and October.

In the letter, seen by the Irish Independent newspaper, O'Leary reportedly promised a pay rise and a "productivity/loyalty bonus" and "significant improvements" in terms of contracts and career path. Pilots have been offered a bonus of €12,000 (£10,700) and O'Leary has also promised to exceed the salaries offered by rival airlines.

The Ryanair also apologised to pilots for the disruption caused by the changes in rotas, after he described them as "full of their own self-importance".

In the letter, O'Leary reportedly pledged to learn from the mistake that has affected the airline over the last couple of weeks and stated there will be "significant changes to, and investment in, our rostering and pilot career development" over the next six months.

"If you have or are considering joining one of these less financially secure/or Brexit challenged airlines, I urge you to stay with Ryanair for a brighter better future for you and your family," O'Leary wrote towards the end of his letter.

In the middle of September, the Dublin-based airline said the shortage of pilots forced it to cancel between 40 to 50 flights a day until 31 October, affecting approximately 315,000 passengers across 2,000 flights.

A week later, Europe's largest airline announced it would cancel a further 18,000 flights between November and March, with approximately 400,000 passengers to be affected. It added 34 routes will be affected by the temporary winter suspension, including London Stansted to Glasgow and Edinburgh, London Gatwick to Belfast, Newcastle to Faro, and Glasgow to Las Palmas.

Last week, the carrier contacted the passengers who were affected by its flight cancellations and schedule changes in order to explain their entitlements under EU261 regulations.

The Civil Aviation Authority had given the Irish carrier a deadline to arrange compensation for the 700,000 passengers affected, indicating it could launch legal proceedings against Ryanair otherwise.

According to the regulator, the airline also failed to provide details about its obligations to refund expenses, such as meals and hotels, incurred by passengers as a result of cancellations. The CAA added that while its powers would allow it to fine Ryanair if warranted, it would not be able to issue further punishment, such as stripping the carriers of routes, as the airline is based in Ireland.

O'Leary had vowed to fully cooperate with the CAA but chief executive Andrew Haines warned his promises had to be taken with "a pinch of salt" as he urged the airline to get its act together, adding he was "furious" at the "disregard for consumers and for the law" displayed by Ryanair.