X-37-B hjemme igjen etter 677 dager borte fra hjemmet - Curt Lewis

Mysterious X37-B 'space plane' stays in orbit for 677 days - and no one knows why

A mysterious robotic 'space plane' has now been in orbit for a record 677 days - and America is remaining silent about what it's doing up there.

The robotic Boeing X-37B craft - also known as Orbital Test Vehicle 4 - conducts long missions in orbit, carrying a classified payload.

Observers have speculated that the Space Shuttle-esque vehicle might be designed to destroy satellites - or work as a 'movable' satellite itself.

When it landed from a previous mission, it was greeted by ground crew in biohazard suits - sparking gossip that there was something radioactive on board.

The aircraft has a wingspan of less than 15ft - and is taken into space on a rocket, but glides back to Earth like a space shuttle.

NASA has said that there is a materials experiment on board - but its main payload remains a mystery.

During the aircraft's previous missions, amateur astronomers were able to detect the orbital pattern of the first X-37B which included flyovers of North Korea, Iraq, Iran, Pakistan and Afghanistan, heightening the suspicion that the vehicle was being used for surveillance.