an aircraft having propulsion units for both conventional aircraft flight in the atmosphere and for high - altitude operation as a rocket . the aircraft is divided into a payload compartment and a compartment containing rocket propulsion unit propellant or fuel , and includes a long transverse wing with a small back - sweep to favor lift in the dense layers of the atmosphere and to thus make it possible to climb to high altitudes at a subsonic speed before using the rocket propulsion units . the return flight portion is performed by gliding or controlled as for a conventional aircraft .