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.
"We’re sure these routes will be popular with customers getting away for a UK holiday this summer, as well as those visiting friends and relatives, and we’ll continue to listen to their feedback about where they want to travel," Stoddart added.
BA’s Belfast City-Exeter route will get under way on 16 June flying four-times-weekly on Mondays, Fridays, Saturdays and Sundays.
The Leeds Bradford service will also launch on 16 June operating six-times-weekly on Mondays, Tuesdays, Wednesdays, Thursdays, Fridays and Sundays.
Newquay flights will get under way on 3 July flying twice-a-week on Wednesdays and Saturdays.
Finally, BA’s new Belfast City-Glasgow route will launch on 2 August operating six-times-weekly on Mondays, Tuesdays, Wednesdays, Thursdays, Fridays and Sundays.
