Ryanair has said it will be forced to cut the number of summer flights it operates next year as it predicted further delays before the Boeing 737 Max is allowed to fly again.
The airline said it could be as late as December before regulators clear the aircraft to return to the skies after two fatal crashes.
Ryanair was awaiting delivery of 58 planes before summer but it now expects to receive just over half of those.
It could also close bases as a result.
The airline said it was in talks with airports about which of its hubs could suffer cuts.
“We are starting a series of discussions with our airports to determine which of Ryanair’s underperforming or loss making bases should suffer these short term cuts and/or closures from November 2019,” the airline’s chief executive, Michael O’Leary, said in a statement.
Ryanair added that it would talk to its staff and unions about the planned closures, which it said were “directly caused” by the delays delivering the 737 Max.
The airline is now expecting to carry 157 million passengers in the year to March 2021, five million fewer than it had been planning for.
No Max planes have flown since March after issues with its software were linked to crashes in Indonesia and Ethiopia, which killed 346 people.
Ryanair has a total of 135 of the controversial Boeing models on order, the first five of which are due for delivery this autumn.
It has become the latest airline to cancel flights as a result of the aircraft’s grounding.
On Sunday, American Airlines said it was extending for a fourth time cancellations of about 115 daily flights. The cancellations will now continue into early November due to the continued grounding of the 737 Max.
However, the firm added: “American Airlines remains confident that impending software updates to the Boeing 737 Max, along with the new training elements Boeing is developing in coordination with our union partners, will lead to recertification of the aircraft this year.”
But airlines are still putting in orders for the aircraft. At the Paris airshow last month, International Airlines Group, which owns British Airways, announced plans to buy 200 Max planes at a discount, referring to them as “B737 aircraft”.
Boeing has yet to convince regulators that updates to its software are enough to ensure the Max’s safety.
And last month the US Federal Aviation Administration, which must reapprove the jets for flight, uncovered a new flaw that Boeing estimates will take until at least September to fix.