The airline is starting Covid-19 tests on some flights from Newark airport, near New York, to London Heathrow.

Mr Kirby said it could provide evidence that will convince governments to drop quarantine requirements for travellers.

He said several countries have told United they are interested in using testing to open up their economies.

But these countries "want to make sure everything works" and have said that "health and safety appropriately comes first", he said.

The International Air Transport Association (IATA) says demand for international flights is down about 90% compared with last year.

According to IATA's director-general, Alexandre de Juniac, governments need to "take firm action" to mitigate the economic impact. "The loss of aviation connectivity will have a dramatic impact on global GDP, threatening $1.8 trillion in economic activity," he said.

United is among the many airlines whose fortunes have declined because of coronavirus. It's currently losing $25m (£19m) a day. That compares with a $4.3bn profit last year.

A US government support programme for airlines expired at the end of September, since when United has furloughed 13,000 staff, with another 9,000 leaving on a voluntary basis.