Military Hardware: Tanks, Bombers, Submarines and More At Mach 3, the XB-70 Valkyrie “Lost Pieces Bigger Than the YF-12” — One Test Pilot’s Bar Comeback That Became Aviation Legend In the mid-1960s, Lockheed’s Mach 3 YF-12 and North American Aviation’s Mach 3 XB-70 Valkyrie were both flying test missions out of Edwards Air... Brent M. Eastwood3 hours ago