1999-06-26 - San Fransisco Bay Area, CA - Other

Lenticular object hovering over bay

I saw an object last Saturday 1999 June 26, out over the bay, between the San Mateo bridge and San Francisco. The object was flattened football (lenticular) shaped and white with a slight amount of shadowing underneath it. It was hovering at an angle of about 15 degrees from the horizontal (ie: horizon) but there were no lights visible. I don't know the height exactly, except that it was low enough so that the object from my vantage point looked to be lower than the tops of the buildings in the San Francisco skyline. The sighting took place in the early afternoon, approx. 12:30pm to 1:00pm. The day was mainly sunny but with some smog "fuzzing-out" San Francisco city from my vantage point, but with the buildings / skyline still visible. At first I though it was a dirigible / blimp but it was symmetrical and had no lights / signage on it. Moreover, as I continued to watch it all the way across the bridge, it did not move from its position. At about the half-way point across the bridge, as I observed the object, it did a rather amazing fade-out and became completely invisible. This was not due to cloud shade or the object changing its orientation since the geometry of the object remained exactly as before while doing the fade-out. Immediately after it disappeared, I looked in the sky around the area it had been and at that moment I noticed a commercial airliner flying overhead into the area that the object had just been. As soon as the airliner had traveled a bit out of the area where the object had been, the object did the exact opposite from before and did a fade-in and was exactly as it had been before. The fade-out / fade-in took about the same amount of time, of about 2 to 3 seconds I'd estimate.