In 1955, Pentagon issued a grant for an all-weather attack aircraft. The fuselage is round with large fuel tanks on either side below the wings. Small oval windows are located on either side of the canopy. Tail fin is wide, short, and thick with an identical ventral fin under the fuselage. Short, thin wings are trapezoidal.
Tailplane is swept.
Landing gear consists of a retractable wheel in the nose and a pair of retractable skids in the middle. X-15A made its first flight on March 10, 1959. First flight using the rocket engine was made on June 8, 1959. The fuselage was very long with a pointed nose. The wings were delta-shaped.