And this is interesting...
The Phalanx system has never been credited with shooting down any enemy missiles or aircraft.
February 25, 1991, during the first Gulf War, the USS Missouri and the Phalanx-equipped USS Jarrett were in the vicinity of an Iraqi Silkworm missile (often referred to as the 'Seersucker') that had been fired, either at Missouri or at the nearby British destroyer HMS Gloucester. After Missouri fired its SRBOC chaff, the Phalanx system on Jarrett, operating in the automatic target-acquisition mode, fixed upon Missouri's chaff and fired a burst of rounds (not destroying the incoming missile). From this burst, four rounds hit Missouri which was two to three miles (5 km) from Jarrett at the time. There were no injuries.[2] The Silkworm missile was then intercepted and destroyed by a Sea Dart missile launched from Gloucester. Incidentally, this is the first validated, successful engagement of a missile by a missile, during combat at sea.
June 4, 1996, a Japanese Phalanx accidentally shot down a US A-6 Intruder. The US plane was towing a radar target during gunnery exercises. A Phalanx aboard the Asagiri class destroyer Yūgiri locked onto the Intruder instead of the target. Both pilots ejected safely.[3] A post accident investigation concluded that the Yūgiri's gunnery officer gave the order to fire before the A-6 was out of the CIWS engagement envelope.[4]
Phalanx is considered inadequate against some modern threats and is being gradually supplemented and replaced by the Rolling Airframe Missile, which has greater range and higher hit probability. The RAM system uses an automated and self-sufficient radar fire control similar to that of Phalanx.