The United States Air Force had an orbiter circling the globe for over two years, and most people didn't even know about it. Dubbed X-37B, the space plane looks very similar to a space shuttle, but it's unmanned and significantly smaller.
After 718 days of orbiting, the Air Force has officially landed the space plane back on solid ground. This is the longest that the space plane has ever spent in space during any of its four missions thus far.
The landing was made in Florida this week and generated a sonic boom that residents could hear from all over the state.
There is still very little known about X-37B and what it has done in space all this time. There are all kinds of theories that the U.S. military is using this space plane for strategizing its own forces, but the more likely scenario is the United States military is simply testing its own technologies in space to see how it works, among those: guidance and control systems, navigation, and testing thermal materials.
There are still several questions, but top secret missions tend to stay under wraps for a while until they're ready to be publicized.