There have been 3 return flights to Amsterdam on a M-F basis as well as Sabena flights operating at the same time both with based aircraft pre 2001.
There have been regular flights to Canada / Florida all summer long pre 2007. NI has all the top tourist attractions Giants Causeway, Titantic etc
It has been stated that most flights certainly EZY are 90% FULL that includes international flights. So although we are punching low at the moment I am quite confident that the dynamics will change soon.
The problem is Dublin is cheaper and offers more destinations and as a bonus good ground transport links.
Dublin is not far off its ceiling while Belfast is at the bottom of the ladder - plenty of room to climb.
All it will take is someone like Norwegian to come into Belfast and offer multiple transatlantic destinations, and the Dublin bubble will start to slowly deflate!!!