Built to Leak Jet Fuel': Mach 3 US Air Force SR-71 Blackbird Was Designed to Leak JP-7 Fuel on the Ground -- The Fuselage Panels Sealed at Mach 3

The SR-71 Blackbird’s fuel drips on the ground aren’t a malfunction—they’re part of the design. Built by Lockheed’s Skunk Works in Burbank, California, the Mach 3+ strategic reconnaissance aircraft is famous for outrunning more than 4,000 missiles and photographing 100,000 square miles of terrain in an hour from 80,000 feet. Officially, its top speed is Mach 3.2, and it’s still the fastest known crewed, air-breathing jet in service. Engineers designed the fuselage panels to expand and seal once the plane reaches Mach 3, accounting for temperature swings. JP-7 fuel is used because it dissolves tank liners and has a very high flash point. Crews therefore start with limited fuel and refuel by rendezvous with an aerial tanker shortly after takeoff.