The F-19 fighter designation has been one of the recurring mysteries of the postwar era. There is an apparent "hole" in the fighter sequence between F-18 and F-20. Was F-19 never assigned to any fighter aircraft as the Air Force claims, or is it a cover for some supersecret "black" project that is yet to be revealed?
All throughout the late 1980s, it was sort of an open secret that the Air Force and the Lockheed "Skunk Works" were working on a project to develop a "stealth fighter" that would be invisible to radar. It was assumed by almost everyone that this project bore the designation F-19, since that designation had apparently been skipped when F-20 was assigned to a Northrop design. In July of 1986, the Testor Corporation of Rockford, Illinois released a $9.95 plastic kit model of what they called the "F-19 Stealth Fighter". Tom Clancy referred to a "F-19 Ghostrider" in his 1986 novel Red Storm Rising as part of a plot involving a future European war.
After years of gossip and rumors, on November 10, 1988, the existence of the Lockheed "stealth fighter" was finally officially revealed by the Defense Department. It turned out to be an attack aircraft rather than a fighter, since it apparently has no air-to-air capability. At the same time, it was also revealed that its designation was F-117. It seems that the F-117 designation has nothing to do with the old fighter sequence which ended at F-111, in spite of rumors that the Soviet fighters under test at Groom Lake conceal their real identity by using call-signs such as F-112, F-113, and so on. During its development and test phase, the Lockheed "stealth fighter" was known strictly under its project name of Senior Trend, and never carried any designation at all, certainly not a designation of F-19. Although the real origin of the F-117 designation is still not known with certainty, it seems to have been derived from the strict security restrictions that were in place at Groom Lake during the flight testing--pilots flying the Senior Trend test aircraft were not allowed to tell anyone what type of aircraft they were flying, and so whenever asked to fill out routine forms that requested identification of the aircraft type they flew they would fill in the meaningless number 117. When the first manual for the Senior Trend aircraft appeared, it had F-117 printed on its cover. Since it would cost too much to have the manual reprinted, the designation later became official.
So it seems that the Lockheed Senior Trend was never known as F-19. So what then WAS F-19? When asked about this, an Air Force spokesman claimed that the F-19 designation had never been assigned to any aircraft because of a fear that it might be confused with the Soviet MiG-19. This doesn't seem plausible, because the designations F-17, F-21, and F-23 had not been skipped.
Another rumor was that F-19 is really the designation of some other super-secret project, one that so black that it will not be revealed for many years. Maybe the mysterious Aurora that has been the subject of gossip, rumor, and speculation for the last decade is actually designated F-19. However, it is still not at all certain that any such aircraft as the "Aurora" actually exists.
It is now known that the designation "F-19A" was officially skipped at Northrop's request. Since the F-5G turbofan adaptation of the F-5F was basically a completely new design, the company wanted to have a new designation assigned to it. The next designation in line would be F-19, but Northrop preferred an even number because the Soviet competitors in the export fighter market of the early 1980s all used odd numbers, and Northrop wanted to stand out from these. So the official "confusion with MiG-19"-story isn't all that far from the truth, although it is certainly rather misleading. It is unlikely that anybody would ever confuse an "F-19A" with a MiG-19, especially because the latter was already obsolete. The F-20A designator was approved despite official recommendation by the USAF Standards Branch (at that time responsible for nomenclature assignments) to follow the regulations to the letter and use "F-19A" for the redesignated F-5G. Presumably this change would also make for better advertising copy--"The Northrop F-20: First of a new generation of fighters", for example. A similar sort of thing happened during World War 2 when the designation P-74 (and perhaps P-73 as well) had been deliberately skipped at the request of the Fisher Body Division of General Motors who wanted their new heavy escort fighter to carry the designation P-75 for advertising reasons.