In an extraordinary move, the airport published an open letter to airlines and passengers saying it was introducing a capacity cap from today until 11 September.
It said: “Our assessment is that the maximum number of daily departing passengers that airlines, airline ground handlers and the airport can collectively serve over the summer is no more than 100,000.
“The latest forecasts indicate… daily departing seats over the summer will average 104,000 – giving a daily excess of 4,000 seats.
"On average only about 1,500 of these 4,000 daily seats have currently been sold to passengers, and so we are asking our airline partners to stop selling summer tickets to limit the impact on passengers.”
In the letter, Heathrow chief executive John Holland-Kaye said Heathrow had seen the equivalent of 40 years of passenger growth “in just four months” as travellers returned.
The airport has been criticised for not recruiting enough staff, but Holland-Kaye said normal levels would be achieved “by the end of July”.
He laid the blame for other staff shortages with airlines: “New colleagues are learning fast but are not yet up to full speed. However, there are some critical functions in the airport which are still significantly under resourced, in particular ground handlers, who are contracted by airlines to provide check-in staff, load and unload bags and turnaround aircraft.”
Last month, an amnesty was granted by the government to allow airlines to cancel departures without losing the take-off and landing slot, but Holland-Kaye said this was not enough.
“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.
“We recognise that this will mean some summer journeys will either be moved to another day, another airport or be cancelled and we apologise to those whose travel plans are affected.”
He warned: “The airport will still be busy.”
