Ryanair cancelled 82 flights on Sunday after admitting it had “messed up” the planning of its pilots’ holidays.

The budget airline will cancel up to 50 flights a day up until the 20 September, affecting thousands of customers, because its staff need to catch up on their holiday entitlements and clear off a backlog of leave by employees before the end of 2017.

The airline said the cancellations would improve its system-wide punctuality, which fell below 80 per cent in the first two weeks of September. A combination of air traffic controller (ATC) delays and strikes, weather disruptions and the impact of increased holiday allocations to pilots and cabin crew were to blame for the cancelled flights.

A page on the Ryanair website details flights cancelled up until 20 September. . Ryanair’s Kenny Jacobs said:

“We will cancel 40 to 50 flights daily for the next six weeks, less than 2% of our schedule, with a slightly higher number initially, as we begin to implement these cancellations.

Most of the cancellations are due to a backlog of staff leave which has seen large numbers of the airline’s staff book holidays towards the end of the year.

The airline is changing its holiday year, which currently runs from April to March, to run from January to December instead.

Rynanair said the shift meant it had to allocate annual leave to pilots in September and October.

“In the event of any disruption or cancellation airlines must ensure customers are fully compensated and every effort is made to provide alternative travel arrangements.”

Ryanair has tried to appease angry customers by publishing lists of all flights to be cancelled until Wednesday, after 82 failed to take off on Sunday.

Liam Grime, consultant for the , says:

“The change in holiday year going from April-March to January-December gives the pilots a nine month window from 1st April to the 31st December in which to get their annual leave entitlement booked and used. We do not know if the mix-up here was as a result of pilots not being aware of the change or if there was some delay in approving/scheduling the holiday requests but, whatever the reason, there is a backlog of leave that needs to be taken. No matter what size business you run, there will always be a problem if too many employees need to take leave at the same time and it takes careful planning throughout the year to ensure that there is no end of year crunch with employees needing to use or lose their annual leave.

“Ryanair, and all companies, should have a thorough holiday booking procedure so that whoever is managing it is able to deal with holiday requests, identify where there may be too many people requesting time off at the same time and follow a strict first come-first serve policy when accepting or rejecting holiday requests. Most employers tend to allow no more than two, maybe three, employees to take time off at any one time and it is perfectly acceptable to have this kind of restriction. It is also within the power of employers to dictate when employees are permitted to take their annual leave to ensure that sufficient cover is available for the amount of work that they have on.

“In this case, had sufficient and proper planning taken place then Ryanair would have been able to assess the potential annual leave crunch and come up with some kind of rota for who is on holiday and when, in order to ensure that pilots are still able to use their annual leave entitlement in the allocated time without having to cancel flights. If it was determined ahead of time that their business demands and flight schedule would not permit all of the annual leave to be taken within this timescale then some pilots could have been allowed to carry over any outstanding entitlement to the next holiday year. This would have avoided the current situation they find themselves in of having to let pilots take their annual leave over a two month period, and thus prevented the cancellation of so many flights and the public relations fallout that has come from this.