US will likely buy or trade slots at LHR from BMI in exchange for a significant inter-Europe-PHL/CLT code sharing agreement (already partially in effect), or possibly from LH. Typically LHR yields are far superior to LGW and US isn't going to be left out after next March. However, competing with BA at PHL for premium O&D passengers isn't going to be an easy task, whereas there is no competition for LGW. CLT-LHR (instead of CLT-LGW) as a major connecting point might work primarily because there is no competition for the route, but the result could be less than acceptable yields due to relatively low premium O&D in both directions.