Yes, I remember National being awarded the MIA-LHR route, and this was a welcome announcement. If I remember rightly, they started with leased Airlift DC-8-54F's N108RD and N109RD, and later 747's (N77773 seen 28.6.72, N77772 2.9.72) and DC-10's were then used (N80NA and N81NA both at LHR 24.3.74).
I also remember Delta DC-8's on the Panam interchange which were actually ex PA aircraft such as N8016 (logged 28.5.70), N8038A (14.4.69), N8148A (7.2.71), N8166A (15.2.69) and N8170A (4.5.69) - ex N803PA etc.
Also, who remembers the short-lived use of Northwest 707's on the MSP-LHR service, again, another PA type service? Was it PA54/55 or something similar? Examples logged @ LHR were N352US (10.1.71) N379US (12.3.71) N371US (31.3.71). Unfortunately, I never got a picture of one of these as my camera came a few months later!
Does anyone have the flight numbers for these routes, as I'd like to include this detail when I upload the Delta and National widebodies this winter.
LHR spotter of yesteryear!