SR-72 Darkstar: The Hypersonic Successor to the SR-71 The SR-72 Darkstar, developed by Lockheed Martin, is rumored to reach speeds of Mach 6—twice as fast as the legendary SR-71 Blackbird. If realized, it would become the fastest aircraft ever built. Designed for intelligence, surveillance, and rapid strike missions, the SR-72 represents a new era where speed replaces stealth. At hypersonic velocity, reaction time becomes nearly impossible. Important Details: • Estimated top speed: Mach 6 • Hype