I had just left tracy, CA traveling west on I-205 towards San Francisco. The sky was a little stormy but there was a clearing in it just ahead. In the clearing I saw what a I thought was a airplane leaving behind chemtrails. When I looked closer I saw that the chemtrails weren't getting longer. The whole object, shaped like a sideways teardrop, was moving right to left (north to south). It moved slowly, about the speed of an airplane and was a tan or off-white in color