The Pakistan Air Force is losing nearly two percent of its 900 aircraft each year to accidents. This is more than ten times the rate of Western air forces. These losses are caused by aircraft that are too old and a budget that is too small to properly train pilots and maintain the aircraft. Most of Pakistan’s 520 fighters are over 20 years old. This includes 157 French made Mirage IIIs and 5s, 178 of 186 MiG-21s (the Chinese F-7 version), and 31 of 77 U.S. made F-16s. There have been some new aircraft put into service. Since 2000, Pakistan has received 46 F-16s and 100 Chinese made JF-17s (similar to the F-16). These planes are pretty safe. Older aircraft tend to crash more often.
Pakistan does not have enough money to buy enough new aircraft to replace all those becoming inoperable because of age. You can refurbish old aircraft and keep them flying for half a century or more. But Pakistan hasn’t got the money for that either. There’s also not enough cash for the spare parts and fuel needed for the training flights needed to keep the 3,000 Pakistani Air Force pilots capable of handling high-performance aircraft safely. In short, the Pakistani Air Force is facing a disaster. Each year more and more of their aircraft become inoperable and their pilots, unable to fly enough to maintain their skill, become less capable.
Neighboring India has more money for new aircraft and training. And, like Pakistan, it is using its Mig-21s much less. The most accident-prone aircraft in both countries is the MiG-21. India built 657 of these under license. This seemed like a good idea at the time. The MiG-21 was an impressive looking and relatively inexpensive jet fighter half a century ago. Only much later, when it became clear that the MiG-21 was not very effective in combat, was it realized that all those spiffy looking MiGs were more liability than asset.
The MiG-21 was difficult to fly and maintain. In the end the MiG-21 was too expensive to maintain and too dangerous to fly. India made a mighty effort to make their MiGs safer to fly but the accident rate was still obviously higher than that of Western aircraft (especially the few that the Indian Air Force operated). The MiGs were called "flying coffins" and gave the air force a lot of bad publicity. India was not the only one, besides the Russians, who had problems with Russian made warplanes. During the Cold War the U.S. had several dozen Russian aircraft they used for training their fighter pilots. Despite energetic efforts to keep these aircraft flying, their accident rate was 100 per 100,000 flying hours. That's very high by U.S. standards. The new F-22 has an accident rate of about 6 per 100,000 hours, mainly because it's new. F-15s and F-16s have an accident rate of 3-4 per 100,000 flight hours. India, using mostly Russian aircraft, has an accident rate of 6-7 per 100,000 hours flown (compared to 4-5 for all NATO air forces). Pakistan’s accident rate is at least three times that of India.
All combat aircraft have, for decades, been getting more reliable, even as they became more complex. For example, in the early 1950s, the U.S. F-89 fighter had 383 accidents per 100,000 flying hours. A decade later the rate was in the 20s for a new generation of aircraft. At the time the F-4, which served into the 1990s, had a rate of less than 5 per 100,000 hours. Combat aircraft have gotten more reliable and easier to maintain, despite growing complexity, for the same reason automobiles have. Better engineering and more sensors built into equipment makes it easier for the user and maintenance personnel to detect potential problems. Aircraft used the computerized maintenance systems, currently common on new aircraft, long before automobiles got them. Unless you have a much older car that still runs, or a real good memory, you don't notice the enormous increase in automobile reliability. But older pilots remember because such changes were a matter of life and death if you make your living flying an aircraft. And commanders know that safer aircraft means more aircraft to use in combat and more aircraft that can survive combat damage and keep fighting.
India is solving the MiG problem by retiring all the older (bought before the 1990s) MiGs. Only the 67 MiG-29s are being kept in service. These aircraft were among a new generation of Russian combat aircraft, appearing at the end of the Cold War, that were built to Western standards. This made a big difference in the accident rate but not nearly enough. The MiG-29 crashed a lot and was much more expensive to maintain, especially compared to contemporary Russian fighters like the Su-27. For decades Sukhoi was the second largest Russian military aircraft supplier, and after the Cold War ended Sukhoi aircraft became the most common. The MiG aircraft appear to be at the end of the line.