I do not know about percentages, but I can say this. I was raised near an US Air Force base near the dessert. When I was about 15 years old some friends and I went to a movie on base ( friends father was pilot ). We had arrived early, before the theater had opened. It was near dusk & were waiting out side in the parking lot. One of us had noticed the lights on base were not on yet, if you are not aware they turn on befor it gets dark. It started to get dark enough to see stars, we started to look at them (the stars). One of us saw something flying very high, east to west and quite fast, and brought to all our attention. As it approach straight over head it flashed quite brightly, making a 90 degree turn due south. It flew out of sight, in a few second after we could no longer see it all the lights on base turned on. I never found out what it was, but I do know it had to be over 5000 feet up and at over 500 knots. After this I did see some unexplainable sights, but this is related to the heading.