Doncaster is in an awkward part of the country for routes I suspect.
I can get to most of the major conurbations (London, Leeds, Manchester, Bristol, Newcastle, Edinburgh & Glasgow) within 4 hours by car - some a lot less.
If I don't want to drive most of these can be done by train also
London, 1h 40m
Leeds, 40m
Manchester, 1hr 30m
Bristol, 3hr 30m
Newcastle, 1hr 30m
Edinburgh 2hr 45m
Glasgow 3hr 45m
Basically taking into account the hassle of flying, the time of check-in and the flight, + dealing with an airport on the edge of a city, the plane route fails. I think it's unlikely that we will see mainland UK routes at the airport.
Sadly when I do want to fly - typically to Ireland, the routes aren't there and I end up with a drive to East Midlands or Leeds.
It would be great if Doncaster could pick-up a route out to a hub though.
In the meantime I look forward to the new link road, living just 1 minute away from it's terminating point.