This is a harsh reality check.
If a low cost airline with rock bottom introductory offer prices can't make a go of it, it just ain't going to happen.
Northern Ireland just isn't a big enough or important enough place to sustain regular flights to the US, other than House of Mouse flights for the school summer holidays.
If a place like Birmingham can't sustain regular flights to the USA, what hope NI? The West Midlands has a million more people in it than the entire population of NI.
Most air passengers in NI are flying to GB - the rest to the med. That's it really - that's what people want.