What was it doing and why did it stay up there so long? And why is no one talking?

Was it watching us? Was it listening to us? Was it messing with us?

At least we know this … the The US Air Force’s unpiloted X-37B space plane landed back on Earth Sunday after a record 780 days in orbit, racking up the fifth ultra-long mission for the military’s mini-shuttle fleet, Space.com reported.

The X-37B’s Orbital Test Vehicle 5 (OTV-5) mission ended with a smooth autonomous touchdown at the Shuttle Landing Facility of NASA’s Kennedy Space Center in Cape Canaveral, Florida at 3:51 a.m. EDT (0751 GMT), Air Force officials said. The mission originally launched on a SpaceX Falcon 9 rocket on Sept. 7, 2017.

With the successful landing, OTV-5 broke the previous X-37B mission record of 718 days set by the OTV-4 mission in May 2017. OTV-5 is the second X-37B mission to land at NASA’s Shuttle Landing Facility, with previous missions landing at Vandenberg Air Force Base in California, Space.com reported.

“The safe return of this spacecraft, after breaking its own endurance record, is the result of the innovative partnership between Government and Industry,” Air Force Chief of Staff Gen. David L. Goldfein said in a statement. “The sky is no longer the limit for the Air Force and, if Congress approves, the US Space Force.”

The USAF has at least two reusable X-37B spacecraft in its fleet, and both have flown multiple flights. The solar-powered space planes were built by Boeing and feature a miniature payload bay to host experiments or smaller satellites. They were originally designed to spend up to 240 days in orbit, Space.com reported.

“The X-37B continues to demonstrate the importance of a reusable spaceplane,” said Secretary of the Air Force Barbara Barrett said in the same statement. “Each successive mission advances our nation’s space capabilities.”

Air Force officials have said that the exact nature of X-37B missions are classified, though they have dropped hints about the types of experiments OTV-5 performed in orbit. One payload was the Air Force Research Laboratory Advanced Structurally Embedded Thermal Spreader, an experiment designed to “test experimental electronics and oscillating heat pipe technologies in the long-duration space environment,” according to an Air Force statement.

OTV-5 also flew to a higher-inclination orbit than previous X-37B flights, suggesting it had new experiments or technology tests in store. In a statement today, Air Force officials confirmed OTV-5 carried multiple experiments and carried smaller satellites into orbit, Space.com reported.

“With a successful landing today, the X-37B completed its longest flight to date and successfully completed all mission objectives,” Randy Walden, Air Force Rapid Capabilities Office director, said in the statement. “This mission successfully hosted Air Force Research Laboratory experiments, among others, as well as providing a ride for small satellites.”

The X-37B space plane was originally developed by NASA in 1999 to serve as a technology test bed for future spacecraft and looks much like a miniature version of  a space shuttle. In 2004, the military’s Defense Advanced Research Agency (DARPA) took over the project, ultimately turning it over to the USAF’s Rapid Capabilities Office a few years later, Space.com reported.

X-37B vehicles are 29 feet (8.8 meters) long, 9.5 feet (2.9 m) tall and have a wingspan of just under 15 feet (4.6 m). Their payload bays are about the size of a pickup truck bed, about 7 feet long and 4 feet wide (2.1 by 1.2 m).