Five years ago, the U.S. Air Force planned to retire its 33 U-2 reconnaissance aircraft by 2010. But that didn't happen. Congress blocked the retirement plan, believing that U.S. troops in Afghanistan needed all the recon aircraft they could get. It turned out that the U-2 could, indeed, be very useful to the troops below. Equipped with very powerful sensors, the U-2 pilot, while cruising at 22,500 meters (70,000 feet), are able to see tiny details (smaller than an individual man) on the ground below. The U-2 pilot, in direct radio contact with air force ground controllers who accompany army combat units, can quickly shift their sensors, and aircraft, to areas of interest, or need. If ground troops run into some Taliban, and a U-2 is in the air, it can be quickly overhead, relaying detailed descriptions of what the Taliban are up to.
The U-2s were to be replaced by Global Hawk UAVs. Both aircraft are similar in size and carry similar sensor packages, but the lack of a pilot enables the Global Hawk to stay in the air twice as long (24 hours.) The air force was buying over 40 Global Hawks to replace the U-2, and several other recon aircraft. The U-2 has been in service for half a century, while the Global Hawk is just entering regular service, after nearly a decade of development. The Global Hawk has similar sensors to the U-2, and the UAV operators can also speak with ground controllers. But despite this equality in capability, the piloted U-2s tended to do a better job of providing this direct support to the troops. What the U-2 pilots were doing was similar to what fighter pilots, flying at about 7,000 meters, do using their targeting pods.
Even as the air force planned the U-2 retirement, they were putting a new model into service. The U-2S Block 20 model has a digital "all glass" cockpit. That means that nearly all the information the pilot needs can be obtained from three 6x8 inch multifunction displays, and two smaller ones. With these displays, a lot of additional information can be displayed, like checklists, and a moving map to show where the aircraft is (it flies at up to 22,500 meters altitude.) The new electronic systems contained more self-diagnostics and software that helps the pilot quickly figure out problems, and solutions to them.
With a range of over 11,000 kilometers, U-2s typically fly missions 12-18 hours long. All U-2s are being upgraded to the Block 20 standard, and kept at least until the robotic RQ-4 Global Hawk is completely debugged, and available in sufficient quantity to replace all the U-2s. In service since 1955, but always in small numbers, meant that fewer than 900 pilots have qualified to fly the U-2.