Norwegian Airlines is looking to cut up to 259 jobs at Gatwick.
Pilots and cabin crew are in talks with the airline, which say it will try to save as many jobs as possible.
The airline say the Covid-19 pandemic continues to severely impact the business and notes that the "prolonged crisis" is far from over.
The pilots union Balpa says it's yet more evidence of the "devastating effect Covid-19 is having on global aviation".
Norwegian Airlines say it will continue to operate short haul flights from Gatwick.
The pandemic continues to severely impact our business and this prolonged crisis is far from over. These unprecedented circumstances require us to review the London Gatwick crew base in line with current business needs and the associated costs going forward. We have entered into consultation with our crew colleagues and unions in the UK.