London Heathrow airport said it has begun cutting front-line jobs after a recovery in passenger numbers was delayed by Britain’s introduction this week of a quarantine rule for incoming travelers.

Europe’s busiest airport will initially seek voluntary departures after agreeing a severance plan with unions, it said in a statement Thursday. The hub has already eliminated 500 management posts.

The quarantine plan has sparked uproar among U.K. airlines and airports, with carriers led by IAG SA saying they’ll mount a legal challenge. Heathrow Chief Executive Officer John Holland-Kaye warned previously that the 14 days of self-isolation for arriving passengers would put one-third of the hub’s 7,000 posts at risk if Britain failed to say when the policy might be lifted.

“Throughout this crisis, we have tried to protect front line jobs, but this is no longer sustainable,” he said in the release. “While we cannot rule out further job reductions, we will continue to explore options to minimize the number.”

A Heathrow spokesman said the airport has 5,500 front-line workers but that the number of job losses hasn’t yet been determined while it consults with labor groups.

Security, Maintenance

Posts affected will include security officers, baggage-trolley operatives and engineering and maintenance staff. A third of the airport’s 1,500 management positions were cut previously.

Heathrow, the main base for British Airways, directly employs only about 10% of the 76,000 people who work at the hub across 350 companies including airlines, retailers and ground handlers, as well as in roles such as immigration and air-traffic control.

Aviation trade groups separately expressed relief as Britain issued guidelines for the resumption of air travel that broadly follow International Civil Aviation Organization measures including the wearing of face masks and social distancing at airports, while omitting steps such as as blocking middle seats.

Airlines UK and the Airport Operators Association both welcomed the recommendations, though International Air Transport Association vice president for Europe, Rafael Schvartzman, said in a statement that the guidelines will be “rendered useless” if the quarantine policy is retained.

Test and Trace

Quash Quarantine, which represents 500 travel and hospitality firms, cited a survey of more than 2,000 Britons as showing 70% favor test and trace procedures over quarantine measures, while 59% support so-called travel corridors permitting unfettered travel to and from low-risk countries.

A separate study from Oliver Wyman suggests 75% of British business people expect to travel the same or more once the pandemic ends, and that almost two-thirds of people plan to make at least the same number of leisure trips. At the same time two-fifths would like the green light the government.

Heathrow’s passenger traffic remained 97% down from year-ago levels in May as the coronavirus lockdown grounded flights across most of the world. The quarantine rule means that “grim picture” is set to continue even as some airlines seek to revive flights, it said. Cargo volumes were down 40% last month, with a jump in dedicated freighter flights easing the decline.