Flybe will in February add a fifth weekday service from Belfast City to Glasgow and a fourth weekend service from Belfast City to London City.
From February 2, the extra Glasgow frequency will see an additional morning departure and a new early afternoon return on weekdays.
The additional LCY frequency on Saturdays and Sundays will operate in the afternoon. It is also scheduled to start on February 2.
Flybe CCO Paul Simmons said: "We have been pleased with the strong performance of this route [Belfast City to LCY] since it started at the end of October.
"Our passengers know that extremely quick and convenient access to the heart of both Capitals makes complete business sense. Adding an extra daily flight will help even more."
Also on February 2, Flybe will begin a year-round service between Belfast and Liverpool (see news, November 25).