Just a few note on your analysis.
1. The whole aviation industry was in a decline before 9/11. This was used as an excuse by most airlines to cuts routes and frequencies.
2. Gill Airways were the operators on the Aberdeen, Paris and the Belfast and I think the Norwich as well I think. Anyway these routes all went when they collapsed.
3. The load factors on these routes back then were probably lower, bear in mind though a return ticket to Belfast was around £150 return excluding taxes.