Q: Flyover, anyone?

I am trying to play around with the Flyover-feature in Maps on Yosemite, but I cannot find a way to activate it. Sometimes the button appears if I go to Paris, France, for instance, but then I want to zoom in and the button disappears and I cannot find any way to make it reappear. I click everywhere but it is nowhere to be found. Then I close the window and search for Paris again. Sometimes the button appears and sometimes not. It should be a menu item, IMO, but there is none. Is my hardware too old? Late 2009 iMac.