AER Lingus and British Airways owner IAG has announced it suffered a pre-tax loss of €7.8 billion (£6.8bn) in 2020.
This compares with a profit of €2.28bn (£2bn) a year earlier.
Revenues collapsed 69 per cent from €25.5bn (£22.2bn) to just €7.8bn (£6.8bn) last year as the Covid-19 crisis hit.
The number of passengers using IAG's airlines remains significantly down on pre-pandemic levels, and fell again during the traditional peak festive season.
The company, which also owns Iberia, said capacity for 2020 was just 33.5 per cent of 2019 levels, and is only expected to be around 20 per cent between January and March.
IAG chief executive Luis Gallego said the results "reflect the serious impact that Covid-19 has had on our business".
Getting people travelling again will require "a clear road map for unwinding current restrictions when the time is right", he said.
"We know there is pent-up demand for travel and people want to fly.
"Vaccinations are progressing well and global infections are going in the right direction.
"We're calling for international common testing standards and the introduction of digital health passes to reopen our skies safely."
Mr Gallego said IAG airlines will not require passengers to prove they have been vaccinated against Covid-19.
Testing will be key for travel until vaccines have been rolled out across the world, he added.
Australian airline Qantas has said in future it will require passengers to prove they have received a jab before they can board its international flights.
Mr Gallego said there was a "big increase" in demand for travel after Prime Minister Boris Johnson announced his plan for easing restrictions in England on Monday.
Flight bookings were up by more than 60 per cent compared with the same day during the previous week.
"If we continue with the road map to open aviation, we are going to have positive summer," Mr Gallego said.
He revealed that IAG will contribute to a Government taskforce evaluating how foreign travel can resume.
