How did the USS Vincennes misidentify an Airbus aircraft?
tl;dr We don't know.

The US Government has not made enough information available to answer this question. The official Iranian and US reports contradict each other. Inofficial accounts of sailors on other USN vessels operating in the vicinity at the same time contradict both the official US report as well as statements made by Vincennes commanding officer.

There are several possible explanations, many of which have not been officially acknowledged, and probably, the real cause will be a combination of multiple factors. And some of those are easy to address:


User Interface Design: the target tracking system recycles target designations. Shortly before the shootdown, the system had assigned a new target designation to the aircraft and recycled the old designation for a fighter operating over 100 miles away. When the CO asked what the classification for the target designation was, the answer was "fighter" and that it was descending, which was correct for that target designation, but was actually for a completely different aircraft now.


Don't Do That!

No access to current flight plans: the crew only had access to the standard regular schedule, but not to updated flight plans, e.g. including delays or cancellations. On the day in question, the flight was delayed by over half an hour.


Assets used for monitoring mixed-use airspace should be equipped with civilian radios and be in contact with ATC.

Ergonomic Design: the lights were so dark, and flickered every time the weapons were fired, that the crew assigned to monitor the airspace couldn't read the printed out flight schedules.


Better lighting. Or, put the schedules / flight plans into the computer. Even better: integrate them into the target tracking system.

Timezone confusion: the flight schedules were printed out in Iranian time, but the ship's time was Bahrain.


One word: UTC.

Missing Equipment: the Vincennes had no possibility of using civilian frequencies (other than the international distress frequency 121.5), so they had no way of knowing that the "unresponsive" aircraft was in fact in constant communication with ATC.


See #2. Note that directly after the incident, the US Navy did install tunable VHF radio on all ships in the Gulf.

Wrong Frequency: of the 10 attempts to establish contact with the aircraft, 7 were made on military frequencies. Obviously, being a civilian aircraft, the Airbus had no way of hearing this.


Train crew to remember that failure to respond to a military frequency does not imply hostile intent, especially since civilian aircraft won't even be able to respond.

Speed confusion: when the Vincennes adressed the unidentified aircraft, they gave the aircraft's speed in groundspeed as 350kts, but the indicators in the aircraft would have read 300kts indicated airspeed. Since the speed was wrong, the pilots may have thought the calls were made to a different aircraft operating in the vicinity whose speed was closer to the one in the call.


Make it clear in your transmission that you are talking about groundspeed.

A year earlier, another USN vessel was (mistakenly) hit by Iraqi missiles. Her commanding officers received official Letters of Reprimand, effectively destroying their careers, stating that defense of the ship is the first duty. This may have put the CO under additional pressure, fearing for his and his family's livelihood.


Don't punish people for being hesitant in highly complex combat situations involving close proximity of civilians.

Scenario Fulfillment is a psychological condition affecting both individuals and groups where once a situation looks like a certain training scenario, that scenario will be followed to the end, filtering out all Information that does not fit the scenario. The US Government has put forth the possibility that the entire bridge crew may have collectively suffered from this condition.


Psychological training.

The crew was under stress since they had illegally and unprovoked entered Iranian waters, and were simultaneously also engaged in a firefight with Iranian gunboats (which Vincennes provoked by illegally sending her helicopters into Iranian airspace). Either of these two infractions would have been cause for Iran to send fighters to intercept and attack the ship.


See #9.

The CO was known to be a hot-headed aggressive guy looking for fights, and even creating them if there was none. He may have been looking too hard and found one where there was none.


Don't hire such guys, filter them out using psychological evaluations.