Only three were built. Two crashed killing both Northrop pilots.
Northrop brought two F-20's, one with ordnance and the other for aerobatic demonstration.
I was at the Suwan AB (Korean Airbase), watching the demonstration, and the
F-20 was inverted with its landing gear,and flaps down at about 1000ft. As it rolled the gears were retracted, but the airspeed dropped significantly, causing an inverted stall.
There was no recovery... it flopped around like a leave falling from a tree. The pilot ejected, but being inverted... he hit the ground with such force, I can't tell you what I saw.
The F-20 land just outside the perimeter and was still intact. Because of the rise patties and how the plane just floated down, there was little damage, except for the tail.
"Darrell Cornell was Northrop's chief test pilot in the early 1980s. He was killed on October 10, 1984 at Suwon AB, while performing a demonstration flight for the South Korean Air Force (ROKAF).
The F-20 (N4416T) he was piloting stalled after a series of climbing rolls performed with flaps and gear extended. Cornell was not able to recover the aircraft from the uncontrolled stall."