It's my understanding that this is a test of a new missile defense system that FedEx will possibly outfit its MD-10s with. FedEx Flight 9090 is now doing a short flight out of and back into Manchester, NH. The route of flight is taking the plane into northern Pennsylvania before looping back into New Hampshire. One of the interesting aspects of this flight--if FlightAware can be believed--is the altitude the plane is at during portions of the flight. Over parts of PA this plane is supposedly dropping from 20,000 feet down to around 3,000 feet (!). Interesting nonetheless.
Chris in NH