UFO? Try top secret military aircraft. These are the most mysterious military airplanes, jets and space planes flying today, including the infamous Aurora black triangle, the Boeing X-37, the new Northrop Grumman unmanned RQ-180 stealth drone, the Blackstar space bomber, and stealth Black Hawk helicopters.

These incredible black projects were developed under the watch of the US Air Force, the US Navy, the CIA, the US Army and NASA. With numerous sightings, they've been the subject of conspiracy theories and investigations for decades.

Tested in top secret locations like Area 51, evidence and footage is difficult to obtain but rumors of their existence continue to persist.

So buckle up for a look at the 5 most secret military aircraft, and don't be surprised if you encounter a bit of turbulence...