Stansted Airport is the worst in the UK when it comes to flight delays, according to a new investigation.
Passengers were kept waiting for an average of 25 minutes at the airport last year.
Birmingham and Luton were joint second worse with average delays of 19 minutes each.
The average flight delay across all airports was 16 minutes.
Gatwick had an average delay of 18 minutes and Heathrow 13 minutes.
The analysis of CAA data by the Press Association (PA) found Belfast City (George Best) airport had the best performance with only an eight-minute average delay.
Stansted is the fourth busiest airport in the UK. Most airlines which fly in and out of the London base are low-cost eastern European airlines and Ryanair.
The airport said “adverse weather and air traffic control issues” contributed to the delays.
PA looked at scheduled and chartered flights from 24 UK airports. Cancelled flights were not included.
Rory Boland, editor of Which? Travel, told BBC News: “It’s completely unacceptable for passengers to be regularly delayed by nearly half an hour.
“These delays aren’t just an inconvenience but can leave holidaymakers hundreds of pounds out of pocket because of missed connections, transfers and fines for picking up their hire car late.
“Airlines should stop passing the buck and make it easier for their passengers by finally introducing automatic compensation.”
A spokesman for Stansted said a multimillion-pound investment by Ryanair to support its ground operation at the airport has delivered “improvements to flight punctuality”.
Airport performance, ranked from worst to best
1 Stansted: 25 minutes
2 Luton: 19 minutes
2 Birmingham: 19 minutes
4 Gatwick: 18 minutes
5 Manchester: 16 minutes
5 Jersey: 16 minutes
7 Edinburgh: 15 minutes
7 Belfast International: 15 minutes
7 Southend: 15 minutes
7 Glasgow: 15 minutes
11 Newcastle: 14 minutes
11 Durham Tees Valley: 14 minutes
11 Cardiff: 14 minutes
11 Southampton: 14 minutes
15 Aberdeen: 13 minutes
15 Isle of Man: 13 minutes
15 East Midlands: 13 minutes
15 Leeds Bradford: 13 minutes
15 Heathrow: 13 minutes
20 Bournemouth: 12 minutes
20 Exeter: 12 minutes
20 Doncaster Sheffield: 12 minutes
23 Liverpool (John Lennon): 10 minutes
24 Belfast City (George Best): Eight minutes