Over the last thirty years, the two training programs have developed differently, and the entire concept of "dissimilar training" has changed. The navy kept Top Gun as a program to hone fighter pilot's combat skills. The air force made their Red Flag program more elaborate, bringing in the many different types of aircraft involved in combat missions (especially electronic warfare.) But after the Cold War ended. It became increasingly obvious that none of our potential enemies was providing their fighter pilots with much training at all. In other words, the dissimilar training for U.S. fighter pilots was not a crucial as it had been when the Cold War was going. Actually, it had been noted that flying skills of Soviet pilots was declining in the 1980s, as economic problems in the USSR caused a cut in flying time. During that period, American pilots were getting more flying time. Moreover, U.S. flight simulators were getting better. American pilots were finding that even the game oriented combat flight simulators had some training value. So in the late 1990s, Top Gun and Red Flag found their budgets cut. But the programs remain, as does the memory of why they were set up in the first place. If we find that, say, China is continuing to improve it's combat aviation, gives it's fighter pilots more flying time and their politicians maintain a bellicose attitude towards the U.S., Top Gun and Red Flag can be cranked up again.
Over thirty years ago, in 1969, the navy set up its "Top Gun" fighter pilot school. What made this operation different was that the training emphasized how the enemy aircraft and pilots operated. This was called "dissimilar training". In the past, American pilots practiced against American pilots, with everyone flying American aircraft. It worked in World War II, because the enemy pilots were not getting a lot of practice and were using similar aircraft and tactics anyway. Most importantly, there was a lot of aerial combat going on, providing ample opportunity for on the job training. Not to in Vietnam, where the quite different Russian trained North Vietnam were giving U.S. aviators an awful time. The four week Top Gun program solved the problem. The air force followed shortly with it's Red Flag school.