I would presume it was a military craft, considering your brother's reaction and the assumption that anti-gravity technology is in the government's grasp for quite some time.

I believe your story as I had plenty of vivid UFO encounters. My very first happened outdoor also, as I was playing with a bunch of friends with our flashlights on the night sky. We were in a remote place, and the buzz drew a sizable UFO to our camping spot.

It was dragged by our signals like a moth is attracted to light. The craft was huge and glowing. It stood over the treetops and revolved around them. Couldn't see anything but the size and the glow of the craft.

There are also those orb-UFOs encountered all over the place. I think those are alien in nature though.

I'll leave here an example of another peculiar UFO, reported both over Washington and in NZ - http://alienpolicy.com/teenager-films-ring-shaped-ufo-new-zealand/