An expert warned that the secret space plane X-37B could be used by the U.S. Air Force as a war vessel. Aside from carrying deadly payloads, the X-37B could also be used as a spy satellite.

Developed by Boeing, the X-37B spacecraft is an Orbital Test Vehicle (OTV) mainly operated by the U.S. Air Force. Its orbital missions are focused on demonstrating the reusability of technological equipment used in space.

The X-37B is currently on its fifth mission known as OTV-5. Despite having gone through numerous missions already, not much is still known regarding the spacecraft since the U.S. Air Force is very secretive regarding its details.

For national security and aerospace expert Eric Sterner of the George C. Marshall Institute in Virginia, the high level of secrecy surrounding X-37B could allow the U.S. Air Force to arm the spacecraft with various equipment that can be specifically used for warfare.

“You can put sensors in there, satellites in there,” he said according to National Interest. “You could stick munitions in there, provided they exist.”

The U.S. Air Force has maintained that the X-37B was never equipped with weapons since doing so would be a direct violation of the Outer Space Treaty, an agreement signed in 1967 that prohibits the placement of weapons in space.

Despite this, the U.S. Air Force could still arm the spacecraft with other technological instruments in order to operate as an orbiting spy satellite.

For now, it is not yet clear what X-37B is currently doing in space. Hopefully, authorities will provide more information regarding its mission details.

The X-37B was recently spotted and photographed by a sky watcher and satellite tracker from the Netherlands. According to Ralf Vandebergh, he’s been following the path of the spacecraft since May.

He was finally able to catch a glimpse of it after tracking its path.

“When I tried to observe it again in mid-June, it didn’t meet the predicted time and path,” he told Space.com. “It turned out to have maneuvered to another orbit. Thanks to the amateur satellite observers’ network, it was rapidly found in orbit again, and I was able to take some images on June 30 and July 2.”

X-37B
The X-37B Orbital Test Vehicle waits in the encapsulation cell of the Evolved Expendable Launch vehicle at the Astrotech facility in Titusville, Florida in this April,2010 handout photo provided by the U.S. Air Force. The X-37B is the U.S.'s newest and most advanced unmanned re-entry spacecraft. Reuters/U.S. Air Force/Handout