Perhaps you flew in more than one aircraft, because I’m sure you don’t remember the dry loud noise and props through the window on a turbojet aircraft. DC-7s were still around in the 1960s, though sometimes on less important routes. (In 1965 I flew in a UA DC-7C SMF-SFO.) And perhaps it wasn’t Pan Am? Depending on the year, it looks like PA east-west USA flights were operated by AA. See below 1966.