In looking through my Pan Am and Trans World/TWA timetables covering the years 1970-1991, I noticed that neither airline operated PHL-LHR (and return) non-stop from 1970 until sometime after 1986. The first timetable of either airline in which I find PHL-LHR and LHR-PHL non-stops is the Sept. 1989 edition of TWA. Looks like the service was continued by TWA until the takeover of TWA's LHR routes by American Airlines in 1992.
Was PHL-LHR (and return) non-stop by TWA the result of new route authority for a U.S. carrier... or did PHL-LHR replace LHR route authority from another U.S. city... or did TWA pick-up previously dormant authority for a U.S. airline to fly PHL-LHR non-stop?
Anyone have the date (after 1986) TWA started flying PHL-LHR and LHR-PHL non-stop? Before TWA started this route, were BOAC/British Airways the only carrier holding authority to operate LHR-PHL and PHL-LHR non-stops?
Thanks for any information on this subject.