London's Heathrow said it would cap departing passengers at 100,000 a day this summer to limit queues, baggage delays and cancellations, and it was asking airlines to stop selling tickets for flights that could be curtailed.
Britain's busiest airport, like others across Europe, is struggling to cope as demand rebounds after the pandemic. Heathrow had between 110,000 and 125,000 daily passengers departures in July and August 2019.
Airlines at Heathrow had already responded to a government appeal to cut capacity, but the airport said it needed them to go further.
"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," CEO John Holland-Kaye said in a open letter on Tuesday.
"We have therefore made the difficult decision to introduce a capacity cap with effect from 12 July to 11 September."
"We recognize that this will mean some summer journeys will either be moved to another day, another airport or be canceled and we apologize to those whose travel plans are affected," he added.
The London hub said the cap was in-line with limits implemented at its rivals. Schiphol in the Netherlands has capped passenger numbers about 16% lower than 2019 levels, while Frankfurt has cut flights at peak times from 104 per hour to 94.
Heathrow said the average number of outbound seats still remaining in the summer schedules was 104,000 a day, 4,000 above its cap. It said on average 1,500 of these 4,000 seats had been sold to passengers.
"We are asking our airline partners to stop selling summer tickets to limit the impact on passengers," he said.
British Airways, Heathrow's biggest customer, has already cut thousands of flights from its schedules this summer due to staff shortages.
Heathrow on Monday apologized for the long queues and baggage issues customers had endured in recent weeks, blaming staff shortages across the whole aviation sector.