Saw something flying in the air that did not look like an airplane or any other craft I am familiar with.

My living window is 16 floors up in Northern Virginia with unencumbered views all the way into Maryland. As the crow flies I am 2-3 miles from Reagan National Airport and see tons of airplanes flying through the sky daily. I am familiar with the expected trajectory, speed, and duration of visibility simply through observation. Whatever this was, it was not flying like anything I had seen before.
In addition to circling above while moving west to east, the "craft" itself was rotating and flying very, very fast. The planes I see out my window always fly away from Northern Virginia. This one flew right over head and then disappeared.
When I first saw it, I thought through all possible alternatives before settling on "UFO", and I'm not sure I'm saying I think it was for sure. I thought very large bird? (because of the circling). Marine One coming in for a landing at DCA?