The UK’s busiest airlines have seen a significant increase in flight delays over the last five years, according to consumer watchdog Which?

It looked at Civil Aviation Authority data for the arrival times of 10 million flights between 2014 and 2018.

It found that the number of Ryanair flights delayed by an hour or more doubled in the past five years, from three per cent in 2014 to nearly eight per cent in 2018.

Easyjet also saw an increase from under five per cent in 2014 to almost nine per cent last year. Hungary’s Wizz Air went from three per cent to over six per cent.

Thomas Cook passengers were the most likely to face a delay of at least an hour, with 11.5 per cent of flights arriving at least an hour late.

Ryanair responded in a statement: “These Which? figures are inflated and inaccurate. They refer to 2018, which was the worst year on record for [Air Traffic Control] delays in Europe.”

Easyjet and Thomas Cook also argued the delays were due to factors outside of their control, such as airspace, weather and strikes.

KLM was the least likely to be delayed, with two per cent of flights delayed by an hour or more in 2018.

Budget British airline Jet 2 reduced the number of delays of one hour or more from 5.9 per cent in 2014 to 5.3 per cent in 2018, while also more than doubling its operations.

British Airways also improved its punctuality, with 4.5 per cent of flights delayed in 2018 compared to 4.7 per cent in 2014. However it has seen a number of other issues, including hundreds of flights being cancelled after an IT failure in 2017.

Passengers are currently facing disruption due to a planned pilot strike in September.

Cancelled flights were not included in the Which? survey.

Which? found that Stansted was the worst UK airport for delays, with ten per cent of departing flights delayed by an hour more, twice as many as at Heathrow.

“On-time performance” statistics can prove controversial, with Ryanair judged to be among the most punctual airlines in other surveys that looked at the number of flights arriving 15 minutes late or more. Some also accuse airlines of “schedule padding”, where they increase the stated flight time in order to improve the appearance of punctuality.

Passengers are only entitled to compensation under the EU’s regulation 261 when a flight arrives three or more hours late and the delay is “within the airline’s control”.

When flights are delayed by two hours, the airline must offer assistance in the way of food, drinks or accommodation if required.