Well... I can say earlier this summer as I was standing in my parents farm in northern Wisconsin my brother caught a craft speeding across the sky and yelled look!! It was around 6 PM and still very light outside. If you have ever watched the space station travel across the sky...compare the space station speed of 17,100 mph... this craft, with no contrail... came up from the southern sky with a speed twice or maybe more of the space station. It moved from the south and turned with a very short turn radius of 90 degrees turning from Madison/Wis Dells towards Wausau/Green Bay. The shiny craft moved at least 30,000 mph. It was visible for about 8 to 10 seconds. Of course it was impossible to know its altitude... but, it appeared as though it were at the altitudes of commercial aircraft...
Amazing how advanced weather ballons have become.
;>)