OK so perhaps I was a bit harsh on Skip but, going back to his point re the now American flights from the eastern seaboard destinations, I'd be interested to know how the potential market has changed in the case of each city pair just because one airline has taken over another.
Both company's sales/marketing/operations departments will have made their assessments of the potential for each route and in all but the case of CLT will have factual information.
Given the distances between the US cities involved and the markets they serve and, though US travellers are used to connecting flights, most travellers in those markets would prefer direct flights, if only to save time, hassle and potential delays.
What may happen, if the airline bean counters wish it so, is that the direct flights will be priced out by fare manipulation making a flight from to MAN, with a change of flight over any other of the gateways significantly cheaper than the direct flight. Fellow bean counters, who care little about travel hassles, many of whom have never seen a map since their last geography class in school and even then weren't paying attention, would then immediately issue edicts to their company staff to take the cheaper route.
This might well happen with fare manipulation over JFK where the BA/AA frequency is such that there is constant pressure to fill seats and success between MAN and any eastern seaboard gateway works to the detriment of the Heathrow service, and we all know BA has no interest in MAN.