Yes. I'll never forget it. I was 19 years old and living in Seattle at the time. I saw it in broad daylight along with 100 or so other people. Someone else pointed it out to me and my friend. It was a tiny little pin prick waaaaaay up in the sky. It would hover for a while, then do circular patterns, then dart clear across to the other side of the sky (I have no way to gauge it, but it must have been dozens if not a hundred or more miles in mere seconds). We all watched it for over an hour.

Boeing is big in that area, and I guess it's possible it was some kind of test aircraft, but the maneuvers this thing was doing are unheard of in modern aviation. Some would even say impossible.