Ryanair has announced big cuts to its winter flight schedule, saying it will operate at only 40% of last year's capacity.
It said the cuts were in response to increased flight restrictions imposed because of the coronavirus pandemic.
This had led to "materially" weaker bookings in November and December.
The airline is closing its bases in Cork, Shannon, and Toulouse for the winter, but expects to maintain 65% of routes with reduced frequencies.
"With this greatly reduced winter capacity and load factors of approximately 70%, Ryanair now expects full-year traffic to fall to approximately 38 million guests, although this guidance could be further revised downwards if EU governments continue to mismanage air travel and impose more lockdowns this winter," the airline said.
Ryanair's group chief executive Michael O'Leary said the airline deeply regretted the schedule cuts, which he said had been forced on it by "government mismanagement of EU air travel".
He added: "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.
"There will regrettably be more redundancies at those small number of cabin crew bases, where we have still not secured agreement on working time and pay cuts, which is the only alternative.
"We continue to actively manage our cost base to be prepared for the inevitable rebound and recovery of short haul air travel in Europe once an effective Covid-19 vaccine is developed.
" Airline woes Earlier this year, foreign travel was paralysed for several months by the pandemic, with airlines, airports and tour firms shedding thousands of jobs.
Since then, constant changes to the UK's list of countries subject to quarantine have confused potential holidaymakers and hampered the travel industry's efforts to recover.
Airlines have been cutting costs in an effort to remain viable, with the International Air Transport Association warning that hundreds of thousands more jobs are at risk .
Mr O'Leary has been extremely critical of the UK government's policy on quarantining people arriving in the country from overseas, describing it as "a shambles".
The policy requires travellers to high-risk countries to isolate for two weeks on their return to the UK.
At the same time, he has praised the Italian and German governments for having "a much more aggressive test and trace system".
In his latest remarks, Mr O'Leary called on all EU governments to adopt the European Commission's traffic light system, which allows for safe air travel on a regional basis between areas that have Covid case rates of fewer than 50 per 100,000 people.