My argument was mainly that for NCL-BHX, flybe could offer flights for 1/3 or even 1/6 of the price. If there were "enough" passengers to keep Eastern on the route for as long as they did, paying the fares Eastern charged, then logic (to me) would dictate that more people would pay cheaper fares, espacially when those fares also open the market up to leisure travellers, as well as connecting traffic onto Flybe's other routes from the BHX base
I would also make the same argument for flights from NCL-MAN, it's just a inconvenient to get to from NCL, and I think that as one of the largest airports in the UK, with a good selection of Flybe codeshares on the route, such as Cathay, Etihad and Virgin, I think it could also support itself
If the airport were to back it, offer 30 minute check in with security fast track, then 25/30 minutes on the metro from Newcastle/Gateshead, 30 minute check in, 30/40 minute flight and 10 minutes through to airside... I'd say that was pretty competitive with the train, especially if it was cheaper
Not forgetting the added advantage of being able to check your bags in at NCL and not see them until you land in HKG with Cathay, SYD with Etihad or BOS with Virgin