The YF-23 Black Widow II is one of two prototypes built of the YF-23 by Northrop and McDonnell Douglass the other called YF-23 is called the Gray Ghost. They both were built but the project was canceled. It was entered in the USAF Advanced Tactial Fighter competition losing to the YF-22 later known as the Lockheed F-22 Raptor.

Northrop Frye died on January 23, 1991 at the age of 78.

Northrop Frye died on January 23, 1991 at the age of 78.

The F-18 was based on the YF-17 (the aircraft that "lost" the USAF LWF [Lightweight Fighter Program] ). The YF-17 was a development of the P-530 Cobra (which, in turn, was a roundabout development of the F-5 Freedom Fighter).

All of these aircraft were a product of Northrop, with McDonnell-Douglas providing much input at the stage between YF-17 and F-18 as completed.

The agreement between the two firms was that MDD would produce the naval variants (F-18, which became the F/A-18) and Northrop would produce the land-based versions (F-18L). Unfortunately for Northrop there were no orders for the F-18L.

1. The F-22 had horizontal tail surfaces, whearas the YF-23 did not.
2. The F-22 had a intake situated at the wing root, at the first quarter-line, whearas the YF-23 had a intake situated under the wing proper, at the centreline
3. The F-22 has a maximum speed of Mach 2.25 (1670 mph) at altitude and Mach 1.82 (1350 mph) at supercruise, whearas the YF-23 has a maximum speed of Mach 2.2+ (1630+ mph) at altitude and Mach 1.6 (1185 mph) at supercruise.
4. The F-22 has a wing swept at the front more than at the back, whearas the YF-23 has a triangular wing with a wing swept the same at the front and back.