The fastest dive by a bird is that of a peregrine falcon (Falco peregrinus), which has been estimated as reaching a terminal velocity of approximately 300 km/h (186 mph) when in a diving stoop. At this point the peregrine falcon is the fastest animal. In 2005, "Frightful", a peregrine falcon owned by Ken Franklin of Friday Harbor, Washington, USA, was clocked at 242 mph (389.46 km/h) while stooping (diving after prey) from nearly three miles in the air. "Frightful", then a six-year-old, 40.64-cm-long (16-in) bird weighing 997.9 grams (2.2 lb), had wings opening to a full 104.14 cm (41 in) span.
To clock Frightful's mid-dive speed, Ken Franklin and a few mathematicians and engineers fastened a 113.4-gram (4-oz) computer chip taken from a a skydiver’s Pro-Track recording altimeter/computer to Frightful’s tail feathers and measured how far she fell in a certain time interval.