The U.S. Air Force’s mysterious X-37B space plane has broken its own record during its ongoing secret mission. Despite this, the Air Force is still very secretive regarding the exact nature and objective of X-37B.

On Aug. 26 at 6:43 am EDT, the X-37B spacecraft surpassed the record it set during its previous mission dubbed as Orbital Test Vehicle 4 (OTV-4). After maintaining spaceflight for over 717 days, 20 hours and 42 minutes, X-37B’s current mission OTV-5 is its longest one yet, Space.com reported.

Of course, compared to other known spacecraft especially those from NASA, spending more than two years in space isn’t that impressive. After all, NASA’s Voyager probes have been in space for over four decades now.

Despite this, the X-37B is still very impressive in its own right especially after considering that it is still in its test phase. It is not yet clear what the exact nature of the spacecraft will be once it moves forward to its next stage.

For now, the U.S. Air Force is sticking to general descriptions regarding what they want to do with the spacecraft.

“The primary objectives of the X-37B are twofold; reusable spacecraft technologies for America’s future in space and operating experiments which can be returned to, and examined on Earth,” the military branch wrote in the spacecraft’s fact sheet.

“Technologies being tested in the program include advanced guidance, navigation and control, thermal protection systems, avionics, high temperature structure and seals, conformal reusable insulation, lightweight electromechanical flight systems, advanced propulsion systems, advanced materials and autonomous orbital flight, reentry and landing,” the Air Force added.

Based on the description, it would seem that the X-37B is just like any other modern spacecraft designed by NASA or SpaceX. However, since the Air Force is very adamant about keeping other details of the space plane and its mission a secret, there have been a lot of speculations regarding its true function.

According to Eric Sterner, a national security and aerospace expert at 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.”