Citing CAA data, Which? said around 1.3 million air passenger journeys were subject to severe delay last year.

In the year to June 2018, 13,000 flights to and from UK airports were delayed by at least three hours - equivalent to around 3,500 passenger journeys a day.

According to the data, the worst short-haul offenders were Icelandair with 1.7% of flights delayed by more than three hours, followed by Guernsey airline Aurigny (1.6%) and Tui Airways (1.4%).

Mid-haul, Thomas Cook came off worst with 1.2% of flights delayed for more than three hours, then Tui (1.1%) and Saudi Arabian Airlines (1.0%).

Finally, Norwegian had the highest percentage of three-hour plus long-haul delays (2.4%) followed by Thomas Cook (1.8%) and Tui Airways (1.6%).

Under existing EU regulations, passengers are entitled to compensation if they are delayed by more than three hours when flying ex-UK or with an EU airline to an EU airport.

Compensation ranges from £220 to £360 for short-haul flights, and up to £535 for long-haul - and airlines can claim exemption in “extraordinary circumstances” such as extreme weather.

Which? though is calling for airlines to start automatically compensating passengers for delayed and cancelled flights, branding the existing process “complicated and time consuming”.

Alex Neill, Which? managing director home products and services, said: “Severe delays can be a complete nightmare and totally wreck a long awaited trip abroad, especially if it means you’re stuck in an airport terminal for hours on end.

“Passengers are often entitled to compensation when airlines get it wrong. It is vital automatic compensation is introduced across the industry so people no longer have to jump through hoops to get what they are owed.”