I was in a commercial passenger air plane that had just left the oakland airport, bound for london. it was about 6: 55 pm pst and we had just about reached cruising altitude when i saw it. i was sitting next to a window and i was glancing down at another plane far below us when i noticed a much closer object traveling much faster beneath us. at first i thought it was another airplane but it obviosly looked nothing like an airplane so i thought maybe it was a drone. however it was flying almost as high as our plane which made that unlikely and it obviously wasn't a military aircraft. of course it took me a second to realize that the object had no wings and no exhaust of any kind. it was silver, and reflective like chrome. it was shaped like a tic tac with a more curved and almost pointy end on the front (side in which the object was accelerating). the back side was round with several rings around it sort of reassembling an exhaust port on a rocket but there was no exhaust coming out of it. the object was moving in a straight line but much faster then our plane and the plane much further below us. it moved almost parallel to our plane at a slight angle towards us accept going in the opposite direction before crossing underneath our flight path. i couldn't believe what i was seeing and i couldn't comprehend how it was moving so fast or even flying at all without wings. i wanted to get it on film but it was moving so fast i knew i wouldn't be able to get to my phone in time, plus i didn't want to take my eyes off of it. i watched it for about 15 seconds before it flew out of sight from my window.