The Northrop Grumman/McDonnell Douglas entry into the Air Force's Advanced Tactical Fighter (ATF) competition was nicknamed the Black Widow II. Although it never was able to reach its top speed, computer simulations showed that the YF-23 could attain about 0.1 mach higher than its competitor the YF-22 Raptor. It was also proven to be about 10% more stealthy than the Raptor, and used off-the-shelf parts to help reduce cost, unlike the Raptor which was designed almost from scratch. It had the nosewheel unit from the F-15, and the undercarriage from an F/A-18, as well, but not all of its components were derived from other aircraft. It had an advanced radar, as well as the passive infrared tracking system common on many Russian fighters.
Although the YF-22 did have thrust vectoring capabitlities, it was not jealousy of the Russians that caused the Raptor to be chosen as the winner. The thrust vectoring gave the YF-22 greater low-speed maneuverability (which it can be argued is less of value in modern air combat than additional stealth). But the main reason the YF-22 was chosen over the YF-23 is politics. Northrop's B-2 "Spirit" stealth bomber was delayed, and suffering cost over-runs, and McDonnell Douglas was having trouble with the eventually canceled A-12 bomber, and was also in the middle of its "super hornet" project to upgrade the F/A-18. Lockheed Martin (who designed the YF-22) on the otherhand had developed the F-117 "Nighthawk" stealth fighter (made famous during the Gulf War) on time and under budget. These factors led to the Pentagon ultimately choosing the Raptor not for pure performance, but because of faith in the manufacturer.
The first prototype made its maiden flight on July 7, 1990, and now both YF-23's are owned by NASA, but it is doubtful whether or not they will fly again.
Type: Advanced-technology fighter
Powerplant: The first prototype used two 35,000 lb. thrust Pratt & Whitney YF119 engines, the second variant used two General Electric YF120 advanced technology engines.
Max Speed: Mach 1.6 without afterburn. Mach 1.8 with afterburning "supercruise."
Range: Undisclosed, but more than 2,790 miles.
Ceiling(Maximum Altitude): Over 65,000 ft.
Weapons: Four-Six AIM-7 Sparrow Missiles, or AIM-120 AMRAAM radar-guided, and four AIM-9 Sidewinder heat seeking missiles, plus an M61A1 Vulcan rotary 20-mm cannon.
Weights: Empty-36,900 lbs. Loaded-63,866 lbs.
Span 44 ft.
Length 67 ft.
Height 14 ft.
Wing Area 945 sq. ft.
*Some of the information in this writeup was derived from "Aircraft of the World: A Complete Guide"