Heathrow Airport said its losses widened to £1.5 billion in the first nine months of the year.
Passenger numbers between July and September were down by more than 84% compared with the same period in 2019.
Revenue fell by 72% to £239 million, while earnings before tax and interest dropped to £37 million.
Heathrow chief executive John Holland-Kaye said: "Britain is falling behind because we've been too slow to embrace passenger testing. European leaders acted quicker and now their economies are reaping the benefits.
"Paris has overtaken Heathrow as Europe's largest airport for the first time ever, and Frankfurt and Amsterdam are quickly gaining ground.
"Let's make Britain a winner again. Bringing in pre-departure Covid tests and partnering with our US allies to open a pilot air bridge to America will kickstart our economic recovery and put the UK back ahead of our European rivals."
Heathrow said it had taken "rapid actions" to protect itself when the pandemic struck.
"We have now realised over £200million of our minimum £300million operating cost savings target, and we remain on track to deliver this target by the end of the year," the airport said in a statement.
But it added it now needed to "go further" with the virus proving harder to beat than first thought.
Making people feel safe enough to fly again is key, the airport said.
"In August our colleagues stepped up and took part in trialling three rapid point of care testing solutions," Heathrow said.
"The trials aim to understand how these tests might be quickly conducted outside of a laboratory. Findings have been shared with Government."
The trials come on top of a proposed testing facility in partnership with Collinson and Swissport, which is waiting for a Government green light.
Other options include reducing the length of quarantine, for instance by implementing "test and release" after 5 days of quarantine.
"Without a rapid move to testing, the UK will fall even further behind its European competitors and the economic recovery will fail to get off the ground," Heathrow said.
Heathrow also explained just how badly the virus had hit travel.
"We anticipate traffic to decline by an additional 6.6 million to 22.6 million passengers against our previous guidance in June," it said.
"We are also expecting a larger deterioration in traffic for 2021 with passenger volumes declining 54% versus 2019 to 37.1 million passengers."
