In early 1944, North American submitted a proposal to the Army Air Forces for an improved attack bomber, one which would provide the firepower of the B-25 strafers but with substantially improved performance. It was given the designation NA-98X by the company.  It was intended as a lower-cost alternative to the heavily-armed Douglas A-26B Invader. 

Power was to be provided by a pair of Pratt & Whitney R-2800 air-cooled radials, housed inside new low-drag cowlings and driving a pair of four-bladed propellers. 

The new aircraft had the same armament fit including the 75-mm cannon as the B-25H. 

The first flight of NA-98X took place on March 31, 1944, test pilot Joe Barton being at the controls. He reported better speed and acceleration and a higher roll rate. War emergency power could bring the aircraft to 10,000 in 5 minutes. A maximum speed of 328 mph could be achieved at sea level with war emergency power. 

On April 24, 1944, the NA-98X was taken up for a test flight by Maj. Perry Ritchie and Lt. Winton Wey. During a low speed pass over Mines Field, the aircraft disintegrated in mid-air and crashed, killing both pilots. An investigation showed that both outer wing panels had been ripped off the aircraft during the low-speed pass, the plane having been flown beyond its structural limitations by its crew. Following the crash, all further work on the NA-98X project was abandoned.
