While "Vincennes" was firing on the Iranian gunboats, confusion reigned aboard the ship as the tracking of aircraft in the area had become muddled, between "Vincennes" and other U.S. ships, and on "Vincennes" itself. Crucially, "Vincennes" misidentified an Iran Air Airbus A300 civilian airliner, Iran Air Flight 655, as an attacking F-14 Tomcat fighter aircraft. The Iran Air Flight 655 was climbing at the time, and her IFF transponder was on the Mode III civilian code rather than on the purely military Mode II, as recorded by "Vincennes"s own shipboard Aegis Combat System. After issuing multiple radio challenges and receiving no response from the aircraft,"Vincennes" fired two radar-guided missiles and shot down the Iranian civilian airliner over Iranian airspace in the Strait of Hormuz, killing all 290 passengers and crew on board.