Slow travel when observed, followed by an abrupt direction change with unbelievable acceleration.

I was flat on my patio watching our daughter play in the yard.  A line of decorative trees bordered our property.  
This silver-gray circular object appeared over the trees at an unknown height.  It appeared to be very high, but extremely visible against the clear sky.  I watched as it came overhead.  
At this point I called out to a neighbor to look.  It was not drifting as a weather balloon would do.  Rather, it was straight-line movement.  Before the neighbor could position himself to observe it made an abrupt angle and vanished within five seconds.  
Previously it was at a very slow rate of travel.  
When another neighbor came home I told him of the event.   He suggested I report it to the Weather Bureau at the Burlington airport.  
I did so and the person on duty suggested I report it to the Naval Observatory.  Even with the telephone number given I did not report it. 
I was reluctant to even call the airport, so I just dropped the event.  If it happened today I wouldn't hesitate as there are now so many believers.