Loganair is suspending flights between Londonderry and Manchester less than six months after the route was introduced.
The Scottish airline says it will not operate the daily service between January and May 2020, although some flights will be available at Easter.
Loganair blamed a post-New Year drop off in bookings for the suspension of the service.
The Manchester service was launched from City of Derry airport in May.
"We apologise for inconvenience to anyone who has already booked travel during this seasonal stop in the service," Loganair commercial director Kay Ryan said.
She added: "Our forecasts indicate that bookings will be low over the post-New Year period, so we've taken the decision to take a break on the route from January 5 until May 21, with the exception of some flights at Easter."
The airline said customers who have already booked "are now being contacted and offered a full refund or a transfer to an alternative service to Manchester from either Belfast International or Belfast City".
Earlier this month, councillors at Derry and Strabane District Council - which owns the airport - were told almost £6m is required to ensure City of Derry Airport can continue to operate beyond 31 March 2021.
Councillors have given their approval to request additional money from central government.
Loganair took over the London Stansted route in February, following the collapse of Flybmi, which had operated flights on that route since 2017.
Loganair now operates from City of Derry airport to Southend.
The public service obligation air route, the first of its kind in Northern Ireland, has been in place since 2017.