worst planes? Since the dawn of military aviation, there have been planes that can only be described as lemons (that might even be charitable).
The ultimate lemon could be the U.S. Navy F7U Cutlass, which was probably one of the most accident-prone aircraft in Navy history (25 percent loss in accidents in a brief active career). This was the second Vought fighter in a row to have problems. The F6U Pirate also was a flop the 33 airframes averaged only 31 hours of flight time. Both planes pushed the envelope way past the technology of the late 1940s and 1950s.
And then there was the U.S. Navy F4D which, unlike the simpler A4D (later A-4) Skyhawk, was a very difficult plane to fly. Not only that, as the United States found itself in Vietnam and elsewhere, it was quickly retired. The Douglas F5D Skylancer was cancelled after four pre-production planes were built. They later served as test beds for both the military and NASA.
The General Dynamics F-111 can, in some ways, be seen as a failure. It was supposed to fill several roles: Low-altitude penetration and attack for the Air Force, fleet air defense for the Navy, and close-air-support for the Army and Marines. Only the Air Force version ever reached fruition after a lengthy development process.
The United States is not the only country to have had problematic aircraft development. The British had the TSR.2, which was a Tornadoesque plane which was cancelled with only two prototypes completed. The plane was found to be deficient in range and underpowered, and the Labor Government that won the 1964 elections cancelled the project.
The Russians had problems, too (even though they usually stole designs from the west). For every success like the MiG-15, there were planes that did not fare as well like the Lavochkin La-15, which was a much more complex aircraft. Chinas J-8 Finback (one was famously lost in the April 2001 EP-3E incident) has been fitful, and relegated to service with the Chinese Navy.
The top lemon in the 60 years of jet combat aircraft, however, is out of Egypt. The Helwan HA-300 was supposed to be a Mach 1.7 interceptor. It barely broke Mach 1. The project continued to limp along, with only three prototypes built before Egypt killed the program. These were very bad planes. If sent into combat, to borrow a comment from a Marine pilot about the F2A-3 Buffalo, one should consider the pilot as lost before leaving the ground. Harold C. Hutchison (email@example.com)
People often debate about what was the best warplane ever built. However, there is the flip side to this coin: What were the