Counting up the monthly passenger totals for EXT-BHD in 2019 gives an annual total of just under 35,000 which is in the same area as 2018's total of 36,722.
A daily Ryanair between EXT and Belfast (whether City or International) would provide over 136,000 seats. Ryanair usually looks for 90%-plus annual load factors which would mean at least 122,000 passengers.
On shorter mainly intra British Isles services (ie within the UK and the Republic of Ireland) they sometimes seem to settle for circa 75% on certain routes. 75% of 136,000 is still over 100,000. Given that Ryanair invariably attracts more passengers than someone like Flybe did and at cheaper fares would that still be enough to increase the EXT-Belfast travelling market three-fold?