As far back as the sixteenth century, Leonardo da Vinci explored the possibility of leaping from the ground into flight in one swooping motion. He was dreaming of the helicopter. At the turn of the twentieth century, such pioneers as Igor Sikorsky regarded vertical flight as the only flight worth making. They also realized how formidable were the problems involved in such flight. Two types of aircraft have dominated the development of vertical flight -- helicopters and short takeoff and landing (STOL) aircraft.
