There was about 40plus transferring LHR-MAN -JFK/ORD/PHL from AA this morning. Not sure if AA are overbooking their LHR-US services, but it's becoming in more common for pax to transfer LHR-MAN-US than the other way around.
Isn't that just bizarre! Can you imagine leaving your booking to a company travel agent, or getting a great deal on Skyscanner, who books you through LHR. Only then to get rerouted via your local airport. Bet there's a few 'sod's law' faces!