A secretive US space plane has reportedly set a new record for consecutive time in orbit after spending almost two years on its current mission.

The X-37B Orbital Test Vehicle has now spent a 718th day in space, overtaking the 717-day mark set by the same type of vehicle on a previous mission.

CNN, ABC News and Air Force Times were among the US publications to hail the achievement as a record for time in orbit for a space vehicle.

The plane’s mission continues and no return date to Earth has been announced.

Little is known about what the X-37B is doing in space, and US Air Force has not shared the location of the plane while it is in orbit.

The current X-37B plane in orbit, called OTV-5, was launched in September 2017 on a SpaceX Falcon 9 rocket. It was built by Boeing.

The plane’s unique design looks like a miniature space shuttle - it is just nine metres long and three metres wide.

The vehicle has the ability to modify it's orbit.