Driving home from work. Trying to focus on breath. Looked up in the sky for no reason, noticed after I had ducked my head to see past roof of car (I'm 74" tall). Size and altitude made me think possible aircraft, especially since BWI, Wash. Nat. and Andrews AFB all have potential flight patterns above. I noticed the vibrant reflective properties, and the size and speed made me think that something at that altitude would stall. I noticed what seemed to be a reflection from the sun at only and angle a circular shape could produce, and then total disappearance before my eyes. Nothing blocked my view, and the craft wasn't going fast enough to have sped away from my field of view (again, almost stall speed). I am in so much disbelief and play devil's advocate in any situation where a UFO may have been a potentiality. Disbelief plagues any thought I had previously of a potential UFO. This was no potentiality. uSAP or otherwise, this wasn't your normal aircraft.