Monarch is set to close its engineering base in Manchester, putting 123 jobs at risk.
The airline said that its Manchester airport engineering operation is “less viable” than other hangars in Birmingham and Luton, following a review of its facilities.
A proposal to close its Manchester hangar has now gone into consultation with its employees based there, but the company stressed that no final decision has been made.
Andy Mackay, who is interim managing director of Monarch Aircraft Engineering, said: “We are fully committed to retaining talent, skills and expertise within our business. In the event that redundancies become necessary, we will offer alternative roles to all those affected, with relocation to our other facilities.”
Union Unite branded the announcement as a “severe blow” and added that it believed that some engineering jobs in Luton and Birmingham would also be cut.
Oliver Richardson, Unite’s national officer for civil air transport, said: “18 months ago our members at Monarch made significant sacrifices in terms of their pay, and terms and conditions to help secure the deal with Greybull Capital.
“So it is very disappointing and a severe blow to our engineering members to hear this news when they have played their part in turning around Monarch and making the airline the profitable business that it is today.”
Greybull Capital purchased Monarch from the previous owner, the Mantegazza family, in October 2014.
But Greybull is now assessing the future of the airline, with speculation that Easyjet may be interested in launching a bid for its fellow Luton-based carrier.