Ryanair has said it is to close its bases in Cork and Shannon for the winter.
The move comes as the airline cuts capacity over the winter season from 60% to 40% compared to last year.
Its base in Toulouse in France is also to close and there will also be significant base aircraft cuts in Belgium, Germany, Spain, Portugal and Vienna, it said in a statement.
The airline said increased flight restrictions imposed by governments across the EU, air travel to and from much of Central Europe, the UK, Ireland, Austria, Belgium and Portugal have been heavily curtailed.
This has caused forward bookings to weaken slightly in October, but materially in November and December, it said.
"While we deeply regret these winter schedule cuts they have been forced upon us by Government mismanagement of EU air travel," said Ryanair CEO Michael O'Leary.
"Our focus continues to be on maintaining as large a schedule as we can sensibly operate to keep our aircraft, our pilots and our cabin crew current and employed while minimising job losses," he said.
"It is inevitable, given the scale of these cutbacks, that we will be implementing more unpaid leave, and job sharing this winter in those bases where we have agreed reduced working time and pay, but this is a better short term outcome than mass job losses," he added.
The airline had warned a number of weeks ago that it may be forced to close the Shannon and Cork bases for the winter unless the Government took steps to open up air travel by immediately adopting a new EU traffic light style system that classifies countries based on the level of Covid-19 there.