The dives of Peregrine Falcons have been clocked up to 242 mph on camera.  Rumors of falcons reaching over 300 mph are unproven.  The current record was set by "Frightful" in Washington state.  He is a falconry trained Peales peregrine falcon.  Falcons do not dive straight, rather they spin on their way down, using centrifugal force to increase their speed.