It's a beautiful machine from this angle, with its markings and all the surface detail. If you told me this was a new Imperial fighter for an incoming Star Wars sequel, I would believe you. I'm not surprised people mistook it for a UFO being smuggled across America.
X-47B is a technology demonstrator built by Northrop Grumman for the US Navy, a stealth unmanned combat aerial vehicle with an 18.92m wingspan. It's capable of operating from an aircraft carrier, using its two bays to deliver 2000kg of weapons to any target as far as 3889km away.
For comparison, the current US Navy's workhorse, the McDonnell Douglas F/A-18 Hornet, has a 12.3m wingspan, and it's capable of carrying two air-to-air AIM-9 Sidewinder missiles as far as 2000km. It can carry more weapons than X-47B -- 6214kg -- but that would severely cut its range. 1814kg of bombs plus two Sidewinders and two external fuel tanks will only give it a range of 390 nautical miles (722km).
The next version of this drone is called X-47C. When it arrives near the end of the decade it will be even larger -- with a whooping 52.4m wingspan. That will make it as big as the B-2 bomber. Theoretically, the X-47C will be able to carry 4500kg of armament. [Defense Tech]