Airline says numbers must be reduced at bases such as Stansted and Manchester.
Ryanair has written to UK pilots asking them to take unpaid leave or transfer to other bases abroad, saying they could otherwise join the 9,000 job losses at Thomas Cook.
The airline told its pilots that a “significant surplus of pilots must be reduced” at UK bases including Stansted and Manchester, and that it was encouraging them to take up to 12 months of unpaid leave.
It said that there were limited vacancies for full-time pilots at bases in Morocco, Romania and Hungary.
The memo, sent on Tuesday, said: “With yesterday’s collapse of Thomas Cook with the loss of 9,000 jobs in the UK and potentially a further 13,000 jobs across Europe, we hope that there will be sufficient applications for unpaid leave/part time, so we do not have to resort to job losses at [your base] this winter.”
It blamed the delay to Boeing 737 Max deliveries for the decision. Ryanair had ordered up to 135 of the aircraft for its expansion plans, with the first planes due this year.