July 3rd 1988. The USS Vincennes, the most advanced missile frigate in the US Navy, was patrolling waters in the Persian Gulf, at the end of the Iran-Iraq war. The crew of the Vincennes were engaged in multiple activities – a battle with an Iranian gunboat, which had attacked the ship’s helicopter and monitoring an Iranian military aircraft 60 miles away. At 0947hrs the ship’s Aegis radar picked up a distant blip, alerting operators in ‘Air Alley’, the row of personnel handling air warfare whose task it was to identify any air traffic within range of the ship. The radar system asked the incoming plane: Identify, Friend or Foe? The unidentified plane automatically responded with a civilian call sign. The Navy’s list of commercial flights over the gulf was checked, but no flight for this time and position was found. Discussions ensued as to whether this could be an Iranian warplane. A warning to the plane was flashed over international distress frequencies. The plane seemed too high to be on an attack approach. Further warnings were dispatched and unanswered. Suddenly, the aircraft was noted to be descending and picking up speed; 455 knots with an altitude of 7,800 feet and descending. Was this an Iranian F-14 launching an attack on a US Navy warship? The ship’s Captain had a short decision window as the plane was closing on their position at 5 miles per minute.