Correct name is Sentry and not Centry! I have seen them several times flying in the Netherlands.
On one occasion it was on approach to Valkenburg airbase with grey clouds on the background. When it crossed the motorway I could only see its rotating disk and that was a very strange sight. Car drivers stopped to have a look at this 'UFO flying saucer' and only when I heard jet engines and looked better I realized there was a plane under that saucer!
It even got attention in the newspapers the next day!
