sentences:  Both supersonic services were to be launched at the start of the 1980 summer timetable period.In 1979, the airline took delivery of its delayed third and fourth McDonnell Douglas DC-10-30 widebodied aircraft during the first and third quarter.This permitted the aircraft's introduction on its daily Gatwick—Houston schedule as well as the replacement of the remaining 707-operated services on its mid- and South Atlantic routes.