US Air Force’s mysterious space plane lands after spending 780 days in earth orbit

The US Air Force’s X-37B space plane landed back on Earth on Sunday after spending 780 days in orbit, the longest mission in the mysterious military test program’s history.

The empty plane which looks like a small space shuttle, conducted in-orbit experiments. The exact details of these experiments are a closely guarded secret.

In a statement, the Air Force only revealed that the program “performs risk reduction, experimentation and concept of operations development for reusable space vehicle technologies.”

This is the fifth X-37B space plane to be launched into orbit over the past decade, with each flight longer than its predecessor.

Each mission has been highly secretive, leading to public speculation that the planes could be used for spying activity or testing space weapons.

In a press release Sunday, the US Air Force said the latest X-37B mission conducted experiments for the Air Force Research Laboratory (AFRL). The AFRL develops “warfighting technologies” for the air, space and cyberspace sectors, according to its website. There are speculations of laser weapons being mounted onto it.

Previous missions have tested technologies for navigation, thermal protection systems, autonomous orbital flight and reusable insulation, according to the Air Force.

The planes also have a unique design. They launch into orbit atop powerful rockets and then break away to carry out their mission. When they return to Earth, they touch down horizontally on a runway, like a commercial airplane or space shuttle orbiter coming in for landing.

The plane that just landed was launched to space in September 2017 on a SpaceX Falcon 9 rocket.

The next launch is expected in 2020.