That's incredibly disappointing! I don't understand what is attracting airlines to Belfast city? It is such a small airport and it is really quite far for some people in Northern Ireland.
1. Proximity to the province's financial and political centre.
2. Covenience for the population of south Antrim and Down, comprising > 50% of the population.
3. Lack of any apparent marketing effort, or sense of direction, at International.
4. A demographic that prefers frequency of business-orientated flights over low-cost ( and hence don't traipse down to Dublin ).
5. Various rumours about very aggressive and well-backed marketing at City ( see above ).
For the west and north of the province, Ryanair operate to Stansted from Derry. Makes sense to me that they'd want to put another London pipleline over at the populous and, yes, prosperous east coast.