One of the planes retired from service by the United States Air Force in the 1990s was the F -111. On the face of it, this was a surprising move - as the F-111 had long range (5,432 kilometers) and carried a lot of bombs (36 Mk 82 500-pound bombs or 36 Mk 117 750-pound bombs, or about 70 percent of the load of a B-52). In other words, if you wanted a good tactical bomber, you'd be hard-pressed to do much better than the F-111 or FB-111. Yet these planes were arguably retired before their time, their virtues apparently unappreciated.
However, there were good reasons for the retirement. The sad fact was that the 1990s were the decade of the "peace dividend", and the F-111 did have some vices. First of all, it cost a lot of money to maintain, and that maintenance did not include dealing with unexpected cracks in the wing boxes.
That combination of heavy maintenance (the TF30 engines were not exactly what one would call reliable) and the need for re-manufacturing the wing boxes (a very expensive undertaking) were two huge strikes against the Aardvark's continued operational service.
The F-111 had another big strike against it: The fact that it specialized as a tactical bomber (albeit as a superb one), and wasn't able to handle other roles. That had been discovered the hard way in the 1960s when the F-111B, which was supposed to be an interceptor for the Navy, was cancelled. This was a problem in an era of declining defense budgets. The Air Force was going to have fewer airframes, and each airframe would have to be able of carrying out a variety of missions (the F-15C has the ability - albeit very rarely, if ever, used - to carry just about every variety of air-to-ground ordnance in service).
Versatility was at a premium, and with the F-15E coming on line, and being able to carry a significant war load (12 tons), while also carrying a significant air-to-air capability (four AIM-120 AMRAAM and four AIM-9X missiles), with a decent range (combat radius of 1,770 kilometers), the F-111's fate was sealed. The last bomber version of the F-111 was retired in 1996. The last of the F-111 family of aircraft, an EF-111 Raven electronic countermeasures airplane, was retired from Air Force service in 1998. A few still soldier on with the Royal Australian Air Force, but they will be retired in 2020. - Harold C. Hutchison (email@example.com)