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It was never meant to leave Earth’s atmosphere. It wasn’t designed to be a spaceship, nor was it piloted by an astronaut. But in one of the most bizarre incidents in aviation history, a test pilot in an experimental aircraft found himself on the edge of space—by accident.
The aircraft was the North American X-15, an experimental rocket-powered plane developed during the Cold War to push the boundaries of speed and altitude. Built to explore the limits of high-speed flight, the X-15 was capable of reaching Mach 6.7 (4,520 mph) and altitudes well above 250,000 feet. It wasn’t a traditional aircraft—it had to be carried aloft by a B-52 bomber before being released, at which point its powerful rocket engine would ignite, sending it on a steep climb before gliding back to Earth.
On November 3, 1966, test pilot Michael J. Adams strapped into his X-15 for what was supposed to be a routine research flight. But routine quickly turned into the extraordinary. As the rocket engine roared to life, the X-15 shot skyward at an unprecedented rate. Due to a combination of instrument errors and a miscalculated trajectory, Adams lost control of the aircraft. Instead of leveling off at the planned altitude, the X-15 continued climbing—higher and higher—until it crossed the Kármán Line, the internationally recognized boundary of space, 100 kilometers (62 miles) above Earth’s surface.
At an altitude of 266,000 feet (81 kilometers), Adams found himself in a situation no test pilot had ever faced before. The X-15 was now above most of the atmosphere, where traditional aerodynamics ceased to function. The aircraft, effectively a hypersonic bullet, began to roll uncontrollably, tumbling violently as it re-entered thicker air. Adams fought to regain control, but the forces acting on the plane were too extreme. The X-15 entered a fatal spin, reaching Mach 5 (3,800 mph) as it plunged toward Earth.
At 62,000 feet, the aircraft broke apart, scattering debris across the Mojave Desert. Adams was killed instantly, becoming the first and only X-15 pilot lost during the program. His tragic flight would mark the end of the X-15’s era, but it also secured his place in history: an unintentional astronaut, a man who had left Earth’s atmosphere not in a spacecraft, but in an aircraft.
The flight of Michael Adams remains one of the most harrowing events in aerospace history—a reminder of the razor-thin line between success and disaster when pushing the limits of flight. Though his mission ended in tragedy, Adams was posthumously awarded astronaut wings, making him one of the few pilots to reach space before the Space Shuttle era.