IIRC, Flybe tried MSE - Manchester and subsequently dropped the route. They currently fly from Manston to Edinburgh (daily) and Belfast (3x per week). They have a substantial operation from Gatwick to both Guernsey and Jersey Admittedly not the same airport, but the route from Southend to Jersey operates just once per week.
I'm struggling to think of other routes from Manston that Flybe would want to operate at a sufficient frequency to persuade local Govt to pay a chunky subsidy
Newcastle or Glasgow at a stretch ? Anyone got any other ideas ?