Despite the growing number of Global Hawk UAV reconnaissance aircraft, the demand for high flying spy planes has kept the 1960s era U-2 aircraft in action. This is running the U-2s ragged. Last year, for example, two U-2s, each 41 years old, each achieved a record 25,000 hours in the air. One of these aircraft had made three belly (landing gear up) landings, requiring extensive rebuilding after each incident.
With a range of over 11,000 kilometers, the 18 ton U-2s typically fly missions 12 hours long. All U-2s have been upgraded to the Block 20 standard, so they can be kept in service until the end of this decade. Or at least until the robotic RQ-4 Global Hawk is completely debugged, and available in sufficient quantity to replace it. The U-2 has been in service since 1955, in small numbers. Less than 900 pilots have qualified to fly the U-2 in that time.
The heavy use of the U-2 has been hard on the pilots. Missions can be as long as 12 hours, and pilots operate in a cockpit pressurized to conditions found at 30,000 feet. This puts more strain on the pilots' body. That, and the fact that they breathe pure oxygen while up there, means they tend to be completely exhausted after returning from a long mission.
This wasn't supposed to happen. Four years ago, the U.S. Air Force wanted to retire its 33 U-2 reconnaissance aircraft, and replace them with UAVs like Global Hawk. But Congress refused to allow it, partly for political reasons (jobs would be lost, which is always a live political issue), and because some in Congress (and the air force) did not believe that Global Hawk was ready to completely replace the U-2. This turned out to be correct.
Ever resourceful, the air force has also considered turning the U-2s into UAVs. This is not cutting edge technology, the air force has been turning warplanes into UAVs for over half a century, mainly for use as target aircraft (usually for missile tests, which require very realistic targets if you want to be really sure the missile works.) Replacing the U-2 pilot with software and automated controls also solves several other problems. Since the U-2 only carries a single pilot, the aircraft cannot safely stay in the air as long as it could, because the pilot would become too fatigued. Currently, the max endurance for a U-2 is twelve hours. But without a pilot, and all the gear required by a pilot, you could carry more fuel, and keep a U-2 UAV in the air for up to 18 hours. Moreover, the U-2 can fly higher than the Global Hawk, and carry more sensors. So, in theory, a U-2 UAV is superior to Global Hawk.
The key unanswered question was how much will it cost to develop the software for flying the U-2 remotely, and how long would it take. The answers were too much and too long, so the pilots stayed, and the U-2 continues to get the job done. The big problem was landing, as the long nose and wings make the U-2 very difficult to land. New Global Hawks continue to appear, but there is so much demand for the kind of recon work the two aircraft can do, that both pilots and robots will coexist for a while. At least two years, as the air force now plans to retire its U-2s in 2012, unless Congress intervenes again.