 These advanced aircraft, economically and operationally superior to the 747s and 727s Pan Am operated at the time, were intended to make the airline more competitive.New A300s began replacing 727s on the Internal German Services (IGS) and Caribbean networks later the same year while new A310s later replaced some of the 747s on the slimmed-down transatlantic network following ETOPS certification (approval by the Federal Aviation Administration (FAA) of transoceanic flying with twin-engined aircraft).Pan Am's decision not to take delivery of the A320s and to sell its delivery positions to Braniff meant that the majority of its short-haul US domestic and European feeder routes, and most of its IGS services, continued to be flown with obsolete 727s until the airline's demise.