Europe faces significant disruption to air transport as a growing number of countries bans flights from Britain due to fears over a new coronavirus strain, prompting airlines to repeat calls for more testing to keep borders open.

Eurocontrol Director General Eamonn Brennan said there had been 900 daily flights between Britain and the 27 countries of the European Union between Monday and Saturday last week.

“We’ll see a significant impact on the network as a result of the new (coronavirus) variant in the UK,” the head of the pan-European air traffic control agency wrote on Twitter.

Already reeling from the loss of some six million flights since March due to the pandemic, airlines faced a flood of overnight restrictions echoing the sudden impact of ash from an Icelandic volcano eruption in 2010, albeit on reduced traffic levels.

“The measures came in at extremely short notice,” an airline industry official told Reuters.

Shares in European airlines fell sharply, led by UK-based carriers easyJet, down almost 10%, and British Airways owner IAG, down 9%.

As EU officials met to try to forge a coordinated response, airlines issued a fresh appeal to step up testing regimes in order to keep borders open.

“Governments must cooperate to put mutually recognized testing capacity in place so that borders can remain open to the vast majority of healthy passengers,” the International Air Transport Association (IATA) said.

IATA, which represents most major airlines, said the World Health Organization had adopted a mantra of “test, test and test again” and added: “We implore governments to act on this advice”.

Under initial restrictions, which came into force on Monday, carriers faced a mixed bag of conditions.

Italy and Germany exempted cargo and medical flights from their bans on flights from the United Kingdom, which has said a new, more easily transmissible variant of the coronavirus is spreading rapidly.

Romania also exempted mail flights, but it was not immediately clear to what extent postal services would be hit elsewhere.

Germany’s Deutsche Post said earlier it was halting all deliveries of parcels to Britain.

France, Latvia and Bulgaria banned all flights from Britain with no apparent exemptions, according to notices to pilots. Britain expressed surprised at the inclusion of freight.

Airlines operating in London Heathrow, meanwhile, were warned to ensure passengers do not become stranded in Britain and “can be appropriately routed to the final destination”.

The Netherlands said in an industry bulletin that Dutch carriers and Britain’s easyJet would be able to repatriate aircraft and crew “in order to get these planes out of the United Kingdom”.

Long-haul travel was also affected, though traffic on those routes is already the worst hit from the slump in air travel demand caused by the pandemic.

Hong Kong said it would ban all flights arriving from the United Kingdom from midnight, in the first such move in Asia.

Canada said on Sunday it would halt passenger flights from the United Kingdom for 72 hours.