In a sign of desperation, the CEO of Heathrow Airport has published an open letter pleading with airlines to stop selling flights as he places a cap on daily numbers.

The slot amnesty didn’t really work out. This was designed to encourage airlines to remove flights from their schedules with no penalty.

“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,” he said.

The airport has now implemented a capacity cap, starting Tuesday until 11 September. Gatwick Airport has already imposed one.

The maximum number of daily departing passengers that airlines, airline ground handlers and Heathrow Airport staff can collectively serve over the summer is to be limited at 100,000.

Its latest forecast was 104,000, so 4,000 seats will now be removed each day.

“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,” he said.

Some summer journeys will either be moved to another day, another airport or be cancelled, he added.

Similar measures to control passenger demand have been implemented at other airports, with Lufthansa and Eurowings canceling more than 1,000 flights in July due to airport staffing.

His request follows a similar plea from the UK transport secretary Grant Shapps, who told airlines to stop selling tickets for flights they cannot staff. The UK government is already accelerating national security checks for new airport employees to tackle staffing shortages.

It’s doubtful the new cap will be enough, or that airlines, as well as travel agencies and tour operators, will cut back selling holidays.