The Northrop YF-23 stealth fighter was evaluated with the Lockheed YF-22. Two aircraft were built, PAV-1 and PAV-2. The Chief Test Pilot for the program was Paul Metz, the author of this book. Although the YF-22 was eventually chosen for production, the YF-23 ATF proved to be a very capable and superb example of Low Observable (LO) fighter technology. This book covers origins of the ATF requirement, other manufacturers submissions including alternate Northrop designs, RFI phase May 1981 to May 1982, CDI phase May 1983 to May 1984, ATF DEM/VAL phase 1986 through 1991, Northrop ATF evolution 1971-1986, ATF team, construction, flight test program, engines, summary and selection, NATF proposal, F/B-23 proposal, aircraft nuts-and-bolts, where are they now, program patches, YF-23 pilots, and YF-23 models.