Yep, either the military or a defense-type contractor taking their new toy out for a spin. There could be a lot of reasons they didn't privately fess up afterward (at least that we know of):
* The flight was an "ad hoc training exercise" that wandered a bit too far (ie not specifically approved by higher authority).
* It was a capabilities test to see how well it could do stealthy observing of energy infrastructure in a civilian controlled airspace. While the US doesn't need to spy on its own infrastructure, it's convenient to trial run locally before deploying the capability over Crimea or Venezuela.
* It was a penetration test to measure response to a potential terrorism scenario. If they had warned the airport or police in advance, it wouldn't be an instructive test.
Seems like a weird choice. There's plenty of other air bases that are far removed from the public which are meant to be used for testing. Not to mention there's no justification for doing this in a populated area where someone could get hurt.
* The flight was an "ad hoc training exercise" that wandered a bit too far (ie not specifically approved by higher authority).
* It was a capabilities test to see how well it could do stealthy observing of energy infrastructure in a civilian controlled airspace. While the US doesn't need to spy on its own infrastructure, it's convenient to trial run locally before deploying the capability over Crimea or Venezuela.
* It was a penetration test to measure response to a potential terrorism scenario. If they had warned the airport or police in advance, it wouldn't be an instructive test.