[1] Since this tailless design was novel and considered high risk, it was decided to construct a small, lightweight plane of similar configuration for testing called the Model N-1M.

In parallel with the design of the XP-56, successful flight trials of the configuration were conducted utilizing this airframe, confirming the basic layout.

These trials confirmed the stability of the radical design and, upon review, the Army decided to construct a second prototype, which was ordered on 13 February 1942.

[1] Northrop constructed the XP-56 using magnesium alloy for the airframe and skin, because aluminium was forecast to be in short supply due to wartime demands.

It resembled the GMAW predecessor processes developed in the 1920s by General Electric but, importantly, employed inert gas shielding.

Manual hydraulic brakes were installed and the aircraft flew on 30 September 1943 at Muroc Air Base in southern California.

After a number of flights, the first XP-56 was destroyed 8 October 1943 when the tire on the left gear blew out during a high-speed (~130 mph or 210 km/h) taxi across Muroc Dry Lake.

The pilot, John Myers, survived with minor injuries which he credited to his innovative wearing of a polo player's helmet.

[3] A number of changes were made to the second prototype, including re-ballasting to move the center-of-gravity forward, increasing the size of the upper vertical tail, and reworking the rudder control linkages.