Yes, I certainly have.
When I was a boy, I was badly frightened by what I believe now to be a USAF hovercraft, but to my mind as a child - especially given the actions of the pilot of the craft - I believed I saw a UFO over my head.
I actually wrote a blog post about the experience, though it's been colored a bit differently in my mind after a couple decades of time has passed.
I have spent some time studying the UFO Phenomenon, and my opinions are even now a bit different than when I wrote the blog post. I may have to append some of it, or perhaps i just need to write a Hub about it. :)