Gatwick Airport, London’s second-busiest, is limiting flights this week, partly because of an outbreak of COVID-19 within air traffic control.

In a statement late Monday, the airport said a daily 800-flight limit, affecting both departures and arrivals, has been imposed until Sunday.

Gatwick said around 30% of staff in the division within air traffic control are off sick for a variety of reasons, including COVID-19.

It said the daily cap will prevent last-minute cancellations and delays for passengers while National Air Traffic Services, or NATS, gets back to normal.

Stewart Wingate, the airport’s chief executive, said the decision “means we can prevent as much disruptions as possible.”

The largest number of cancellations will be on Friday, September 29, with 33 departures affected.

NATS apologized to passengers but said that a variety of medical reasons meant it can’t manage the normal flows in and out of the airport.

Though all the COVID-19 restrictions in Britain were lifted last year, people are advised to stay away from work if they have tested positive for the coronavirus.