IAG, the owner of British Airways and Spanish carrier Iberia, dived into a loss totalling 1.3 billion euros ($1.52 billion) in the third quarter on coronavirus fallout, it announced Thursday.
The operating loss before exceptional items compared with profit of 1.4 billion euros one year earlier, IAG said in statement ahead of a full earnings release due next week.
Revenue slumped 83 percent to 1.2 billion euros in the reporting period, it added.
IAG said it expects capacity in the current fourth quarter to be no more than 30 percent compared with a year earlier.
"As a result, the group no longer expects to reach breakeven in terms of net cash flows from operating activities during" the final three months of the year, IAG said.
IAG said bookings had not recovered as expected owing "to additional measures implemented by many European governments in response to a second wave of Covid-19 infections".
It pointed to an increase in local lockdowns, an extension of quarantine requirements for travellers and a lack of pre-departure testing.
New British Airways chief executive Sean Doyle on Monday urged the UK government to end the quarantining of passengers arriving from abroad.
British Airways, which is slashing thousands of jobs, last week announced the sudden departure of his predecessor Alex Cruz.
Doyle had been CEO at Aer Lingus, which like BA, is owned by airlines group IAG.