Four leading airlines have urged the United States and Europe to introduce a coronavirus testing program for passengers to allow the rapid restoration of transatlantic air travel.

United (UAL), American (AAL), British Airways’ parent IAG (ICAGY) and Lufthansa (DLAKY), which carried nearly 650 million passengers between them in 2019, have written to governments on both sides of the Atlantic, urging them to find a way to reopen passenger services.

The letter, signed by the CEOs of the four companies, was sent on Tuesday to US Vice President Mike Pence, the European Commissioner for Home Affairs Ylva Johansson, all EU member states and the United Kingdom.

It cited the “unquestioned importance of transatlantic travel to the global economy” and said a coordinated testing program was “key to providing confidence to permit services to resume without quarantine requirements or other entry restrictions,” according to a copy of the letter shared with CNN Business.

“Covid-19 testing is becoming more and more common throughout the world as a tool to avoid these other more intrusive measures,” the letter said. “Nobody will benefit from a prolonged closure of this most indispensable corridor for global aviation.”

The European Union has barred travelers from the United States from entering the bloc because the country's current coronavirus infection rate does not meet EU safety criteria. The United Kingdom and Ireland require US travelers to go into quarantine.

Airlines hope that by lobbying for a stronger testing regime, they can find a way to restore a major travel corridor even as Covid-19 cases spike in parts of the United States.

The aviation industry is facing the worst crisis in its history. The International Air Transport Association (IATA) estimates the global airlines industry will lose $84 billion in 2020 and an additional $15 billion in 2021, dwarfing the damage caused by the global financial crisis.

IAG, American Airlines and United Airlines, have already warned that as many as 73,000 jobs could go as a result of the pandemic, while Lufthansa said 10,000 jobs were at risk before it received a $10 billion government bailout. British Airways is fighting for its survival, IAG CEO Willie Walsh said last month. United posted a $1.6 billion loss for the last quarter on Tuesday.

London's Heathrow airport, which handled 18.8 million passengers traveling to or from North America in 2019, has called on the UK government to take the lead in developing an international testing standard. It is trialling swab testing for passengers. Several airlines and airports are also trialling testing regimes.

Heathrow's CEO John Holland-Kaye told CNN Business last week that a common international standard for testing is “very logical” and that “testing on arrival as an alternative to quarantine is something that will get the market moving again.”

IATA has recommended testing prior to arrival at the departure airport to limit crowds and potential infection while traveling. It said in a statement on Wednesday that it supports “the goal of reopening the US-EU market safely and swiftly” and that “testing could play a role when we have a solution that is fast, accurate, scalable and affordable.”

“Airline leaders view Covid-19 testing as one of the few strategic options that has the ability reduce further damage to the already suffering global air travel sector,” said Alex Macheras, an independent aviation analyst. “Ideally, testing would be completed in a rapid, reliable way prior to departure. The goal is for an airline to be able to declare a flight as ‘sterile’ or ‘Covid-free’,” he told CNN Business.