Yet these people are unlikely to be entitled to a penny in compensation.
Delays of one hour or more with Ryanair have more than doubled in the past five years, from three per cent in 2014, to nearly eight per cent.
Easyjet also saw an increase from under five per cent in 2014 to almost nine per cent last year.
The same could be said for Wizz Air who went from three per cent to over six per cent.
But Thomas Cook passengers were the most likely to face a delay of at least an hour, with a one in nine (11.5%) chance of getting back from their holidays at least an hour late.
Thomas Cook, Ryanair and EasyJet have all increased the number of flights they operate by between 30 per cent and 70 per cent since 2014, according to the CAA data.
When it came to the airports, Stansted was the UK’s worst for delays by some margin — with more than twice as many departing flights delayed by an hour than at Heathrow, the busiest airport in the country.
Delays at Stansted have been getting worse every year for the last five years — and passengers now have a one in 10 chance (10%) of being delayed by an hour or more.
At Heathrow, the number of flights delayed by an hour or more is just four per cent.
EasyJet and Thomas Cook both claimed factors beyond their control were to blame for the delays, such as airspace, weather and strikes, while Ryanair claimed Which? figures were “inflated and inaccurate”.
A Stansted airport spokesperson said it had posted significantly improved results in the first quarter of 2019.