Air Force to Launch Secret Space Plane Tomorrow--But Don't Ask What It's For

When it comes to keeping secrets, the U.S. Air Force knows how to stay mum. On Thursday, the Air Force will launch its secret space plane, the unmanned X-37B aircraft, from Cape Canaveral. The project has been a decade in the works and cost millions of dollars to develop--but we civilians have little idea what it's for. Once launched via an Atlas V rocket, the plane is expected to spend days or weeks orbiting Earth and performing classified experiments before landing back in California. If successful, the launch will fulfill the Defense Department's long-time dream: