Flight Level 600 (FL600) is 60,000 feet, an altitude well above the "service ceiling" of almost all commercial airliners, which typically top out at FL410 to FL450. In 2026, the primary aircraft operating above FL600 are military jets, high-altitude reconnaissance drones, and specialized research planes. Famous examples include the U-2 Dragon Lady, which can cruise above 70,000 feet, and the Global Hawk UAV. Some modern supersonic "low-boom" demonstrators, like the NASA X-59, are designed to test flight profiles in this rarefied air. Historically, the Concorde was the only commercial jet to routinely reach FL600. Today, certain "high-performance" business jets like the Gulfstream G700 or the Bombardier Global 8000 can reach FL510, but going beyond FL600 requires specialized engines and pressure suits for the crew because the "Armstrong Limit" (the point where water boils at body temperature) is approximately 63,000 feet. Spacecraft like the Virgin Galactic VSS Unity also pass through this level during their climb to the edge of space.