Air Force's X-37B Robot Space Plane: Secret Mission may go on longer

After nearly seven months of flight, the U.S. Air Force's latest X-37B robotic space plane is nearing a milestone in its supersonic super-secret mission in Earth orbit as it chalks up air mileage and operational experience.

As of last week, the re-usable X-37B space plane had been in orbit for more than 206 days, two months shy of its 270-day mission design lifetime.

The spacecraft, which looks like a miniature space shuttle, launched on its clandestine mission on March 5 from Cape Canaveral, Fla.

The space plane is the second X-37B spacecraft built for the Air Force by Boeing's Phantom Works and carries the name Orbital Test Vehicle 2, or OTV-2.