To add to Skipness' comments, I think most people forget just how small NI actually is. The entire population of NI is just 1.7 million - around the same as a small English county.
The vast majority of flights and passengers are to GB.
The economy is dominated by the public sector in a way that would embarass many an Eastern European state and public spending is on the way down. It also has a massively seasonal holiday market (July basically).
Comments on these boards about there being 'markets' to x y and z are largely flights of fancy.