Pure white, floating 747 or 737.I was traveling from Salt Lake City, Utah to Mesquite, Nevada. I was going down I-15, when I noticed a huge jet going NE. It looked like a 747, to me. As I watched it, I noticed something unsettling. The jet was pure white, with no markings anywhere, whatsoever. I was looking for a Presidential seal actually, because Bush was a lame duck, and I thought he might be sneaking in a trip to Zions National Park, which is a short drive from Cedar City. However, the longer I looked at the jet, the weirder things go. I mean, it was only about 200 feet up, traveling below the line of a mesa...and, it was going about 50-75 miles per hour, AT MOST. Also, it should be noted that the local airport there was (A) not in the area of the jet, and (B)it just looked like it was FLOATING, not flying. It made no noise.I am posting this, as I read of someone on your site who saw something very similar. I continued to watch it...then, thought it may be a good idea to watch where I was going. I looked up again, and it was gone.I was absolutly flabbergasted. I know a jet when I see one, and they are usually higher than 200 feet, and they usually fly more than 50 mph, don't they???