I can recall a trip (TWA 747) from Heathrow to Chicago in 1988, where we taxied out past a grounded Comet used for fire training (had this been G-APDT ?), and taxied in at O'Hare past another Comet, N999WA. It seemed a surprising coincidence at the time to pass two of the type a continent apart when they had otherwise long disappeared from life. Both were long-time servers with Mexicana.