It means up to 1,500 passengers scheduled to fly out of Heathrow every day from now until mid-September will see their flights cancelled and a further 2,500 airline tickets a day currently on sale will be withdrawn.

Over the past few weeks departing passenger numbers have regularly exceeded 100,000 a day with repeated reports of “unacceptably” long queue times, delays for passengers requiring assistance, bags not travelling with passengers or arriving late, low punctuality and last-minute cancellations.

Last month, the Department for Transport and Civil Aviation Authority wrote to airline and airport chief executives asking them to “review plans for the summer” to ensure expected passenger levels could be managed safely and minimise further disruption.

Ministers subsequently implemented a slot amnesty programme to encourage airlines to remove flights from their schedules with no penalty.

Heathrow chief executive, John Holland-Kaye, said: “We held off putting additional controls on passenger numbers until this amnesty process concluded last Friday and we had a clearer view of the reductions that airlines have made.

“Some airlines have taken significant action, but others have not, and we believe that further action is needed now to ensure passengers have a safe and reliable journey.”

Gatwick Airport set a daily passenger number cap several weeks ago amid travel chaos caused by airlines cancelling thousands of flights last minute. Today’s cap from Heathrow aims to restore some order for those still travelling through the airport amid a chronic shortage of ground staff and baggage handlers.

Mass layoffs at the start of the pandemic when international travel was all but suspended have left airlines and airports woefully under-resourced and struggling to hire enough people to cope with the sharp rebound in demand for holidays abroad. Holland-Kaye said Heathrow had seen the equivalent of 40 years of passenger growth in just the past four months.

‘Daily drip-feed of disappointment’

Consumer group Which? branded the “daily drip-feed of disappointment” as “hugely unsettling for individuals and families”.

Guy Hobbs, acting editor of Which? Travel, said: “While this cap may ease the unacceptable chaos passengers are facing at the UK’s biggest airport, thousands of people will now be worrying about whether their flight or holiday plans are about to fall apart.”

Heathrow estimates that airlines, airline ground handlers and the airport can safely manage an absolute maximum of 100,000 passenger departures a day.

The latest forecasts indicate that even despite the amnesty, daily departing seats over the summer will average 104,000 – giving a daily excess of 4,000 seats.

Holland-Kaye said: “Around 1,500 of these 4,000 daily seats have already been sold to passengers, and so we are asking our airline partners to stop selling summer tickets to limit the impact on passengers.

“Our colleagues are going above and beyond to get as many passengers away as possible, but we cannot put them at risk for their own safety and wellbeing.”

With thousands of customer complaints flooding in, consumer group Which? carried out two separate investigations into British Airways and easyJet, alleging the airlines were failing to inform passengers of their compensation rights and that they could secure a replacement seat on the earliest flight to their destination if their flight was cancelled.

Hobbs warned: “Heathrow must work with airlines to quickly provide clarity on which flights are being cut, and airlines need to be upfront with those passengers affected about their right to be rebooked at the earliest opportunity, including on services from other airlines.

“Airports and airlines need to be held to account for the unacceptable disruption travellers have faced in recent months. The government must give the Civil Aviation Authority stronger powers so it can hit operators with heavy fines when they flout the rules.”