I was star gazing in my yard just after 9pm and there was heavy air traffic into and out of the local SF/OAK area airports. I saw a faint white light to the south and it immediately struck me that it was too high to land but was flying right over top of the incoming jets. Even though it appeared to be maybe 30k feet high, it was moving almost 3x faster than a normal jet. I began to think that I may have spotted something strange so I watched it quickly race across the sky in a straight line from around San Jose up to Hayward. It didn't make any noise and it never blinked. The light wasn't bright, it was kind of a faint light with no trails. It never got brighter or changed color, just a steady dull white glow. It flew a very straight line and I kept watching it until it was a couple miles north of me. As I was watching, I blinked my eyes a couple times and when I looked again it was gone and I could not see it in the sky although there was nothing to obscure my vision. It silently flew from South to north emitting only a steady light and a very fast speed then it simply disappeared or turned off it's light. If it was an airplane, it did not have legal lights on it and it was travelling at 2-3 times the rate of an airliner and flying over SFO/Oakland airport traffic at an altitude of at least 30,000'.