Illuminated object that seemed to change shape flying over The Strip at nightI was on the rooftop of a night club (on Las Vegas Blvd. near W. Tropicana) when I noticed a strange slightly illuminated shape in the distance. My first impression due to the object's shape and speed was that someone had let off a large cluster of helium party balloons and the wind was carrying them. I thought the hotel and street lights along The Strip were illuminating the object. A few minutes later, I looked up and noticed the object was a bit closer and I became a bit more curious as I began to see some detail. First, rather than being a cluster of objects (aka balloons), it seemed like a more continuous mass where parts of the object had a dull glow of various intensity that changed, as if there were slowly moving parts that were rotating as the object moved forward. The object was about half the size of a fist at arm's length at the closest point as it passed. The object's flight path seem to run parallel along The Strip during the first 10-15 minutes after I first spotted it. And its velocity seemed constant - it moved very slow. In fact, it was pretty breezy outside, so I would think a mass of balloons would be drifting by faster and moving erratically assuming the wind speed was constant higher up. The precise movement of this object gave me the impression as if "it" was spying on the activity of The Strip below. It seemed to be positioned right above The Strip but fairly high up. As the object moved further north along The Strip, passing by the building I was on, the lights remained about the same intensity. Again, it's as though certain parts of the object would move every once in a while, causing some of the lights to shift. I could see where from a distance, someone would classify the shape as a diamond at times due to the main illuminated areas being on the ends of the object. However, the shape seemed to change as the lights moved (or illuminated parts moved?). If I were to assign a color to the object, it was a dull mottled color, lighter than a gray, almost like a tan or light brown.! I point ed out the object to a few friends and joked around that it was a UFO coming to join our party. However, my friends were not very sober and lost interest quickly. I, on the hand, was completely sober. I had celebrated a friend's event the night before, so I had decided to take it easy and drink non-alcoholic beverages all night. I noticed at some point, the object made an abrupt turn and started heading westward. The lights did not change as the object moved over an area off The Strip which was not as illuminated, again suggesting the object had its own light source. As the object went further west, it became too small to see and was out of view eventually. The entire sighting was about 20 minutes. Being the rational person I am (I have a B.S. in Biology from a top university) and with all the literature I've read on the UFO phenomenom and common explanations such as military craft, I thought this might have been one of those private, experimental craft that some hobbyists like to build (they look like hang-gliders with propellers). I've read a couple stories where some jokers flew in unison with these craft with lights stringed across and tried to fool the public into believing they saw an extraterrestrial UFO sighting. Anyway, it was 3am, so if it was some kind of trick, someone was motivated. Alternately, it could have been a military craft, e.g. unmanned aerial vehicle, on a test run, considering LV's proximity to nearby installations.