USAF SR-71 Blackbird Long-Range Strategic Reconnaissance Aircraft. Developed by Lockheed's Skunk Works to cruise at Mach 3.2 at over 60,000 feet. Powered by 2 Pratt & Whitney J-58 engines designed to operate continuously in afterburner. The distinctive vapor trail in subsonic flight is fuel leakage from shrinkage of the titanium exterior panels. Mach 3+ produces exterior skin temperatures of 600 degrees F. USAF Photo.