Airline bmi today announced a restructuring involving a reduction in planes and routes and the possible loss of at least 600 jobs.
The carrier, formerly British Midland Airways, said job reductions would come from all areas of its business.
Bmi said: "The number of full-time equivalent jobs at risk of redundancy is expected to be approximately 600. However further job cuts cannot be ruled out."
Announcing that it was suspending loss-making routes, bmi said it was reducing the number of planes in its international operation from 39 to 30.
Flights from Heathrow to Brussels, Tel Aviv and Kiev, as well as to Aleppo in Syria, will be suspended in January and the service from Heathrow to Amsterdam will be suspended at the end of the current winter timetable period in March.
The seasonal services from Heathrow to Palma and Venice will not be reinstated in summer 2010.
Today's announcement by bmi, which was taken over by Germany's Lufthansa Group earlier this year, follows an announcement earlier this month of 158 job losses at the airline's no-frills operation, bmibaby.
Today, bmi said it was restructuring its international and regional operations "against a background where the airline industry is facing the challenges of a downturn in demand and the worst recession in the UK since records began".
The carrier went on: "In addition to cost-saving initiatives, the programme also includes a wide range of revenue enhancement initiatives."
As far as the expected job losses were concerned, bmi said: "Management has today commenced consultations with unions and staff representatives with a view to minimising the number of compulsory job losses wherever possible."
The bmi group of airlines currently employs around 4,470 people.
Brian Boyd, national officer for civil aviation for the Unite union, said: "Today's announcement is further indication of the difficulties in the airline industry.
"However, the fact that another 600 jobs are being lost confirms our belief that far too many employers are treating people's livelihoods with impunity.
"Unite understands the need to cut costs but job losses seem to be the knee-jerk reaction. To cut jobs so close to Christmas is at best insensitive."
He went on: "Unite met with bmi today and will continue to do everything possible to reduce the need for compulsory redundancies and explore options to keep the pension scheme open.
"Only six months after (bmi founder) Sir Michael Bishop received £360 million from the sale of bmi to Lufthansa, the changes that we suspected for some time are now happening.
"The uncertainty that comes with this news also casts doubts on other bmi operations, including its regional airline business in Aberdeen. We will be seeking assurances on the future of this important base."