Loganair is to take over the London Stansted route from City of Derry Airport following the collapse of flybmi.
The Scottish airline had already stepped in to take on five other UK routes operated by flybmi - three from Aberdeen and two from Newcastle.
Derry City and Strabane District Council, the owner of City of Derry Airport, confirmed the decision, five days after flybmi went into administration.
The route is supported by British government funding through a public service obligation (PSO).
The subsidy, which has been in place since 2017, was the first of its kind in Northern Ireland.
The route will resume on Wednesday 27 February, with Loganair using a 49-seat Embraer 145 jet aircraft.
Mayor of Derry City and Strabane District Council John Boyle said Loganair's appointment was a "very positive outcome" for the airport.
"Securing a replacement operator for this important route within such a short period of time is testament to the commitment of council, the airport and the Department for Transport to ensure there is air connectivity between Derry and London," he said.
"This was a very complex process that has now been successfully completed and we are very pleased to be in a position to appoint Loganair to operate this significantly important route."
Britain's Transport Secretary Chris Grayling said: "It is a testament to the hard work of Derry and Strabane Council, the City of Derry Airport and my department that we have been able to secure a replacement airline so quickly.
"This route is vital because it strengthens the Union, protects choice and boosts trade and travel opportunities - enabling business trips to and from Derry within a day."
Jonathan Hinkles, Loganair's managing director, said: "We're extremely pleased to be selected to operate the essential Derry to Stansted air service following completion of a competitive tender process.
"I know the news about flybmi created great uncertainty, so we're focused on recommencing operations as quickly as possible."
Last week, Mr Grayling confirmed the Government will continue to provide the PSO funding until 2021.
Like flybmi did, Loganair will operate two return flights a day from City of Derry to Stansted from Sunday to Friday, and one return flight on Saturdays.
Loganair already operates a Glasgow service from Derry.
British Midland Regional Limited, which had operated 17 regional jet aircraft on routes to 25 European cities, cancelled all flights from Saturday.
Loganair and Ryanair are now the only airlines serving City of Derry airport.
In 2016, the Northern Ireland Executive pledged #7 million to the loss-making airport, stressing the need to maintain air connectivity from the north west of the region.