London Gatwick Airport moved to limit the number of planes coming and going from its runway for the rest of the week, the airport’s CEO Stewart Wingate said in a statement, marking the latest major disruption at the U.K.’s second-biggest airport.

The reason, the airport said, was that 30% of NATS staff, the group operating Gatwick’s air traffic control, had been forced off work with “a variety of medical reasons including covid.”

Gatwick is now operating under a cap of 800 flights running through the airport each day, a limit which will stay in place until Sunday. That amounts to 164 fewer flights than were expected to operate this week, according to Gatwick’s statement.

“This has been a difficult decision but the action we have taken today means our airlines can fly reliable flight programs, which gives passengers more certainty that they will not face last-minute cancellations,” Gatwick CEO Wingate wrote.

“We are working closely with NATS to build resilience in the control tower, and this decision means we can prevent as much disruptions as possible.”

The BBC reported that 82 flights would be canceled this week, with the airport still determining which flights would be affected.

Easyjet most affected

EasyJet, the airport’s most used airline, is expected to be the most affected, the BBC reported, though British Airways and Ryanair are also expected to be caught in the riptide.

In a statement to Fortune, easyJet CEO Johan Lundgren called the cap on flights through Gatwick “regrettable” but conceded it was the right option to avoid further delays and cancellations.

“Gatwick Airport and NATS now need to work on a longer-term plan so the resilience of ATC [air traffic control] at Gatwick is improved and fit for purpose,” said Lundgren. 

Gatwick has been gripped by weeks of delays and cancellations due to NATS staffing shortages, often with little notice to passengers. 

One airline passenger told the Independent earlier this month that his flight was diverted from Gatwick to Bournemouth as the plane was beginning its descent. The man, named Richard, told the paper he was then forced to sit on the runway for three and a half hours.

In a statement on its website, NATS said its operational resilience would improve as staff returned to work and Gatwick moved out of its busy summer season. 

It added that a new group of qualified staff was expected to come through the ranks, though cautioned this wouldn’t be immediate.

“Even an experienced air traffic controller takes at least nine months to qualify at Gatwick and very few are able to do so, as Gatwick is such a busy and complex air traffic environment,” the group wrote.

Sick days in the U.K. hit their highest level for 10 years this year, according to a newly published study by the Chartered Institute for Personnel and Development (CIPD). 

The study revealed that U.K. workers took an average of 7.8 sick days in the last year, an increase from 5.8 sick days before the pandemic. The trade group blamed the rise on stress, COVID-19, and the cost-of-living crisis.

Air control systems failure

Prior to the latest staffing-induced crisis, NATS suffered an air traffic control systems failure on Aug. 28, causing 1,500 flights to be canceled and hundreds more to be delayed.

Ryanair’s outspoken chief executive Michael O’Leary labeled a subsequent report into the matter by NATS as a “whitewash” that “ridiculously understates” the number of planes affected by the outage.

As the latest crisis began to unfold two weeks ago, O’Leary called on NATS’s CEO Martin Rolfe to step down.

“Airlines are paying millions of pounds to NATS each and every year and should not have to see their passengers suffer avoidable delays due to UK ATC staff shortages,” O’Leary wrote.

“We call on Martin Rolfe to immediately resign and hand the job over to someone competent enough to do it.”