And now the giant Stratolaunch — the largest plane ever built and Microsoft co-founder Paul Allen’s project to lift rockets into the stratosphere before they are launched into space — is on the move. In video released by Allen, the twin-fuselage behemoth can be seen barreling down a runway at California's Mojave Air & Space Port, reaching a speed of 46 mph in a taxiing and ground-handling test. Click here for details from News 2