Services to Exeter, Glasgow, Newquay and Leeds Bradford will be added over the coming months.
BA will operate 18 flights a week between the destinations.
The routes will operate alongside existing BA services between Belfast and London City and Heathrow airports.
BA CityFlyer will operate the routes, which lead in from £48pp one-way.
Tom Stoddart, managing director of BA CityFlyer, said the routes would enhance BA’s regional network and maintain "vital connections" between Northern Ireland and other key UK destinations.
