Today, the U-2 is still flying over Afghanistan, and is expected to fly until around 2023. In the late 1990s, Lockheed Martin performed stress tests on some U-2s to determine the fatigue of the airframes. It turned out that the Dragon Lady has a long fatigue life—75,000 hours—mostly due to its lengthy loiter time at high altitudes, where turbulence is minimal. Even the highest-time U-2 airframes, according to Pocock, are only just approaching 30,000 hours.
Paul Hoversten is the executive editor at Air & Space/Smithsonian.