Almost a quarter of the near two million flights to or from the UK between April 2015 and March 2016 were delayed by 15 minutes or more, affecting around 43 million passenger journeys.

The new analysis from campaign group Which? found that of the 449,000 flights, more than 10,000 were at least three hours late.

This means nearly one million passengers could be in line for compensation under the current EU Denied Boarding Regulation, which excludes circumstances such as extreme weather or airport strikes.

The Which? analysis found that 183,000 long haul passenger journeys were delayed by at least three hours, while 729,000 short haul flights were behind schedule.

Southend Airport was named the location where passengers were most likely to be delayed on short haul flights – 1.7% of journeys were delayed by three or more hours.

Gatwick and Manchester Airports suffered the most delays to long haul journeys, with 1.3% of journeys delayed beyond three hours.

When it comes to short haul flights, Vueling (1.9%), Loganair (1.6%) and Auringny (1.3%) were named the airlines with the highest percentage of delays of three hours or more.

And well known operators Thomas Cook (6th), easyJet (10th), and Thomson Airways (11th) also performed poorly in the short haul delay rankings.

Passengers travelling with Pakistan International Airlines, Air India or US Airways were most likely to face three hour delays on long haul flights. The average delay time for a Pakistan International Airlines flight was nearly 45 minutes.

Alex Neill, Which? director of policy and campaigns, said: “Arriving at the airport to discover your flight has been delayed is incredibly frustrating, and something thousands of holidaymakers will encounter this summer.

“We know that tens of thousands of passengers on late running flights aren’t claiming the compensation they’re due and so we encourage people to claim what they’re rightly entitled to.”

Your flight delay rights explained

You are covered under the Denied Boarding Regulation if you travel to or from an EU airport, on an airline based in the EU.

Under this regulation, if your flight is delayed, you may be entitled to meals, refreshment, phone calls and email and overnight accommodation, depending on the circumstances.

You may also be able to claim for compensation, depending on how long the delay is and how far you’re flying. However, if the airline can prove the delay or cancellation was cause by ‘extraordinary circumstances’, you won’t get compensation.

Long haul travellers could be entitled to £250 (€300) if their plane lands between three or four hours late, or £510 (€600) if their flight was at least four hours behind schedule.

Passengers flying short haul are also potentially eligible to claim up to £210 (€250) if they are delayed by more than three hours.

To claim compensation for a delayed flight, you can fill out the free Which? template – but don’t go through a claims management company as they will eat up a share of your refund.