Right now, there are about 10 or so planes circling San Francisco in non-airport flight patterns and at a variety of heights. It's not Blue Angels. SF has been de-militarized for as long as I've lived here.
I used to live in DC where planes, helicopters, shock trauma airlifts, ambulances, presidential motor brigades, foreign dignitary police escorts, navy blue modified chevy tahoes and metrobus re-routing were almost daily occurrences.
I ran out to the deck like a little kid to investigate what sounded like thunder and found twinkling lights overhead. Then momentarily worried that we were at war and that nobody bothered to tell San Francisco.
If you live here, you understand that it's entirely possible.
Off to bed.