For the second time in the last five months, a Predator UAV has crashed in eastern Afghanistan. Unmanned aircraft have a much higher accident rate than other aircraft, which is largely the result of not having a pilot on board. A pilot can sense things, and take action more quickly and accurately to save the aircraft. UAVs also operate longer on missions, and are single engine aircraft, both of which increase the probability of loss.
The RQ-1 Predator had an accident rate of about 30 per 100,000 hours earlier this year. Now it's over 40. But air force statisticians point out that Predator, and other UAVs, are too new to have established reliable accident rate data. In another few years, that will be the case for the Predator, which is, by then, expected to have a loss rate of 25 per 100,000 hours, and eventually 15. Older model UAVs had much higher rates (up to 363 for the RQ-2A). But these high accident rates have come way down in the last decade. UAVs are expected to follow the experience of manned warplanes in this area.
For example, the new F-22 an accident rate is about 6 per 100,000 hours. 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.) The Indian rate had been over ten for many years, and it is still that high, and often higher, with other nations (including Russia and China), that use Russian aircraft designs. The B-52 has the lowest accident rate of (less than 1.5 per 100,000 flying hours) of all American heavy bombers. The B-1s rate is 3.48. Compared to the supersonic B-1 and high-tech B-2, the B-52 is a flying truck. Thus the B-52, despite its age, was the cheapest, safest and most reliable way to deliver smart bombs.
New aircraft always have higher accident rates, which is how many hidden (from the design engineers and test pilots) flaws and technical problems are discovered. The F-22 is expected to eventually have an accident rate of 2-3 per 100,000 flight hours.
Combat aircraft are becoming more reliable, even as they become more complex. For example, in the early 1950s, the 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 under 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 are a matter of life and death if you make your living driving an aircraft. And commanders know that safer aircraft give them more aircraft to use in combat, and more aircraft that can survive combat damage and keep fighting.