London’s Heathrow airport urged the British government to set out a strategy for resuming flights following a tightening of travel curbs that it says has essentially shut down travel.

Requiring two Covid-19 tests for all arrivals, along with 10 days of quarantine that some must spend in a hotel, means the U.K. border is “effectively closed,” Heathrow said in a statement Thursday.

Chief Executive Officer John Holland-Kaye said the airport is working with the government “to try to ensure this complex scheme is workable.” He called for Prime Minister Boris Johnson to set out a plan for the safe restart of international travel when the government presents its road map for easing the latest lockdown on Feb. 22.

While all airlines and airports have taken a battering in the coronavirus crisis, Heathrow has suffered more than most, with long-haul markets expected to remain shuttered for months. Passenger volumes at what was previously Europe’s busiest hub fell 89% in January, with February expected to be even more challenging, according to the airport.

Holland-Kaye said the government also needs to provide support to ensure the sector can survive the pandemic, including 100% relief from business rates and an extension of furlough funding in next month’s budget.

Frankfurt airport, one of Heathrow’s biggest rivals, posted an 81% drop in passenger numbers last month, owner Fraport AG said separately Thursday.