The U.S. Air Force had its safest flying year in its history, with only 17 Class A (costing a million dollars or more) accidents (and eight destroyed aircraft) in 2009 (which ended in September.) The next safest year was 2006, with 19 accidents (and eight destroyed aircraft). Last year there were fifteen destroyed aircraft. The air force attributes this improved safety record to more crew training, and insisting that crews operate by the book and adhere to procedures. This includes pre-flight planning as well as when in the air.
Another important factor is advances in engineering and maintenance. Aircraft are designed and built to fly more reliably, a trend that has been going on for decades. In line with that, aircraft maintenance has become more effective. Ironically, the safest aircraft is the oldest one. The B-52 has one of the lowest accident rates (less than 1.5 per 100,000 flying hours). The more recent heavy bomber, the B-1, has a rate of 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. The F-22 is expected to eventually have an accident rate of 2-3 per 100,000 flight hours. This part of a trend. 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.
Unmanned aircraft have a much higher rate, which is largely the result of not having a pilot on board. The RQ-1 Predator has an accident rate of about 30 per 100,000 hours. Older model UAVs had much higher rates (up to 363 for the RQ-2A).
Since Vietnam, combat losses have become very rare, and most of those are more a result of accidents (flying too low while shooting at the enemy) than enemy action (ground fire). Smart bombs enable American combat aircraft to fly above it all (over 5,000 meters up) and still deliver smart bombs as needed. The USAF has dominated the air since World War II, and no one has yet figured out how to successfully challenge this air superiority.