Ryanair said it may lose €850-950m in its current financial year, which ends on March 31.
Covid-19 restrictions cut the low cost airlines passenger numbers by 78% in the last three months of the year, showing a third quarter loss in its financial calendar of €306m.
"Covid-19 continues to wreak havoc across the industry," the airline said in a statement. "FY21 will continue to be the most challenging year in Ryanair's 35 year history."
Group chief executive of Ryanair, Michael O’Leary said he expects a dramatic recovery this Summer on the back of a successful vaccine rollout in the UK where 50% of the population should be vaccinated by the end of March.
However, he said the airline accepts that Easter this year will be a "write off" because of delays in the vaccination programme but said that millions of people should be travelling to the beaches of Europe in July, August and September.
Speaking on RTE radio’s Morning Ireland, Mr O'Leary, called on the Government and NPHET to "get its finger out", saying that vaccination is the way out of this situation.
He added that most of the international travel that NPHET worries about is "coming across the border with the North of Ireland' and not coming on non-existent flights at Dublin airport.