On Wednesday October 10, from 6:56 pm to 7:00 pm, or 4 minutes, I watched a single light cross the early evening sky here in San Diego, California. I was viewing this sighting from about one mile north of the San Diego International airport. There were some clouds, but I still could see about 70 percent of the sky. This single white or slightly blue-white light was traveling slowly SW to NE; slower than the commercial jet. I first saw this single light south of me and it flew almost directly overhead, but slightly east of me and then continued in a straight line NE till I could not see it any longer. It was traveling just above the lowest fluffy clouds. After it passed me, while heading NE, it went just above a small cloud at the same time that a commercial jet which was traveling through the same cloud. The jet was flying west to east preparing to turn around east of the San Diego Airport and then land. They were not very far apart; but I don't know how far apart. They basically were in the same cloud. I could easily see the front white light of the commercial jet as well as the wing lights and collision lights before it went into the cloud. The single light had no collision lights. At this time of night, the sky was not black, but a blue black. Not only could I see the lights on the commercial jet, but I could still see the outline of the wings, the body of the jet and the tail section. The single light did not have any wings or anything visible other than the light itself. I am sure I would have been able to see wings if this single light or craft had wings. The single light was less than a quarter the size as the outline of the jet. Again, the single light or craft passed just above the cloud and the commercial jet went through the cloud. They crossed paths at that time. I did see both crafts continue on their paths after they crossed. The single light or craft made no noise. I could hear the jet. The single light was closer to me than the jet.