We know this because the radar operators are on record in many mainstream media interviews telling us the radar can track these objects performing in these ways. Also, why do you doubt that the radar can tell the difference between an object at 80,000 or one at 20,000? Our entire system of air traffic control would fail if they couldn't do that. But, I will tell you, you are wrong, it could not be a meteor. Meteors don't hover at 20,000 feet for hours, nor do they suddenly decide to shoot back up out of the atmosphere after spending hours hovering at 20,000 feet. Do you have another guess?