CX (or the H.K. government) would have to obtain approval from both the U.S. and the U.K. SQ (or rather, Singapore) would have to get the U.K. to open up Heathrow. SQ has permission to fly Europe-U.S. (as they have with AMS/FRA routes to EWR and briefly ORD). The U.S. is o.k. with SQ operating LHR-U.S. but the U.K. government wants to protect BA and VS. MAN-U.S. is o.k. with the U.. government but not LHR-U.S.