I don't believe that UFOs are alien ships, but I have seen two things I can only call UFOs twice in my life.
The first one was when i was probably 12 or so and it was at night. There was a large cirgar shaped light in the sky that separated into 3 pieces and slowly vanished. It didnt seem like it was moving away, it just seemed like the light eating itself up.
The second was in broad daylight and I was in my 20s. I was driving with a friend and we saw a bright light flying over the cascades foot hills between Rainer and St Helens. It was traveling very fast and suddenly went straight up in a 90 deg turn and vanished.
I have been reading about ball lightning lately, and I guess that is one possible exception except there were no storms in the area.
Here is a link to a likely ball lightning sighting.
http://drfong.blogspot.com/2006/12/stra ... tning.html