The United States Air Force space plane has been orbiting the Earth for almost 500 days, but there are no official reports about the details of the mission, or when the aircraft is scheduled to return to Earth.

The United States Air Force space plane has been orbiting the Earth for almost 500 days, but there are no official reports about the details of the mission, or when the craft is scheduled to return to Earth.

This is the third orbital mission for the X-37B plane, which has broken its own record for spending the most days in orbit.

Unlike the space shuttle missions, there is no crew aboard the X-37B.

The National Aeronautics and Space Administration ,or NASA, was originally developing the unmanned spacecraft, but the project was taken over by the Defense Advanced Research Projects Agency in the year 2004.

Astrophysicist Jonathan McDowell is quoted as saying: “I believe it’s testing some kind of experimental sensor for the National Reconnaissance Office; for example, a hyper spectral imager, or some new kind of signals intelligence package.”

There are other speculations about the purpose of the plane, such as international space espionage, or surveillance of countries that are in the path of the spacecraft’s orbit like North Korea, Afghanistan, Pakistan, Iran, and China.