Ryanair has cancelled up to 50 flights a day for the next six weeks after it “messed up” the allocation of annual leave to its pilots.

The budget airline said less than 2% of customers will be affected and confirmed that those who are will be offered either an alternative flight or a full refund.

How did this happen?

There are rumours that Ryanair has been losing pilots to rival airlines including Norwegian, which is building a new hub in Dublin, Ryanair’s back yard. But the Irish operator says it is down to a big administrative error.

Ryanair is trying to squeeze 12 months of annual leave into a nine-month period as it transitions from an April to March holiday year to a calendar one from January 2018.

This has left the airline with a backlog of holidays to be taken before the end of the year following a busier-than-ever summer schedule.

The decision to cancel flights has apparently been made to improve Ryanair’s “system-wide punctuality”, which dropped from 90% to below 80% this month as weather disruptions and air traffic control strikes took their toll.

How many passengers are affected?

Ryanair said less than 2% of flights would be cancelled but this could affect hundreds of thousands of customers.

It cancelled 82 flights on Sunday and 56 flights yesterday (Monday). According to the full list of cancelled flights on its website, there are 55 cancelled today (Tuesday) and 53 tomorrow (Wednesday).

Many of the affected flights are into or out of London Stansted, with a number of flights to or from Birmingham, Manchester, Edinburgh and Dublin also affected.

Many of the affected flights are into or out of London Stansted

What should I do if I'm booked on a Ryanair flight?

Check the operator's website to see if your flight is listed as one of those being cancelled.

If it is, Ryanair should be getting in touch to set out your options. This will be the offer of an alternative flight if there’s one available, or a full refund.

Passengers may also be entitled to compensation under EU Regulation 261, which protects customers when flights are delayed or cancelled and the airline is at fault. The Civil Aviation Authority has some good information on its website.

Ryanair says it has done its best to ensure that the majority of affected passengers will be able to catch an alternative flight on the same day or the following day.

What is Ryanair saying about it?

Michael O’Leary, the airline’s CEO, said: “While over 98% of our customers will not be affected by these cancellations over the next six weeks, we apologise unreservedly to those customers whose travel will be disrupted.

“Ryanair is not short of pilots – we were able to fully crew our peak summer schedule in June, July and August – but we have messed up the allocation of annual leave to pilots in September and October because we are trying to allocate a full year’s leave into a nine-month period from April to December.

“This issue will not recur in 2018 as Ryanair goes back onto a 12 month calendar leave year from 1st January to 31st December 2018.

“This is a mess of our own making. I apologise sincerely to all our customers for any worry or concern this has caused them over the past weekend. We have only taken this decision to cancel this small proportion of our 2,500 daily flights so that we can provide extra standby cover and protect the punctuality of the 98% of flights that will be unaffected by these cancellations.”

What are others saying about it?

Mark Shepherd, head of property, commercial and specialist lines at the Association of British Insurers (ABI), said: “Ryanair has admitted it is to blame for the large number of flights currently being cancelled.

“Travellers affected will be understandably upset and have every right to expect help and support from the airline, whether that is alternative flights with a different carrier or compensation for the disruption suffered and other expenses incurred.

“If passengers are experiencing additional costs which for some reason Ryanair is refusing to cover they may be able to make claims on a travel insurance policy, but this may depend on the level of cover they bought. Clearly the first port of call must be Ryanair itself.”