The Iranians were advised not to let the aircraft take off on it's flight from Bandar Abbas to Dubai - They ignored that advice.

There was Iranian Air Force activity in the area as well as an ongoing maritime incident that involved the USS Vincennes, a USN Aegis Missile Cruiser.

The Aegis System on the USS Vincennes automatically "identifies" and prioritises threats that it "sees" then fires automatically and that is what happened to the Iranian Airbus in 1988. Under the "Rules of Engagement" in force at the time the USS Vincennes was justified in firing.

In the 1960s during the Indonesian confrontation with Malaya, the Guided Missile Destroyer HMS Devonshire was advised enroute to Singapore that attack by Indonesian "Badger" Tu-16 bombers was likely and that it was not known whether or not these aircraft were armed with "stand-off" Kelt Missiles. Devonshire's missile systems relied on manual firing and only the Commanding Officer could give that command. An airborne radar was detected operating in "Search" Mode and the ship went to action stations with both Director and Launcher tracking the target, at this point the General Operations Plot was started. As the target closed to a point where a "stand-off" weapon could be fired the characteristics of the airborne radar went from "Search" to "Acquired" Mode. The Gunnery Officer asked for permission to fire, the Captain refused and stated that he wanted visual confirmation as to the identification of the target aircraft. By this stage the 4.5" Guns on the Devonshire were also tracking the target. After a few minutes the Director Operator for the 4.5" Guns reported - "Aircraft, Aircraft, Aircraft, bearing whatever it was - aircraft identified as Boeing 707 - Civilian aircraft, repeat civilian aircraft". The Captain ordered all weapons systems to train on safe bearings. When the General Operations Plot was examined, the juncture at which the airborne radar went from Search to Acquired the aircraft, the ship and the radar beacon for Kuala Lumpur Airport were in line, the Captain of HMS Devonshire would have been perfectly justified in firing at that point, he chose not to.

Time had moved on a great deal from 1964 to 1988 the Captain of the USS Vincennes potentially faced a far higher threat level and did not have the luxury of choice open to the Captain of HMS Devonshire - It was why the Aegis Defence System was invented.

The Missile system that brought down the Malaysian Airliner is supposed to be used as part of an integrated air defence system designed to protect mobile armoured formations, used as it is supposed to be used and operated the target aircraft would have been identified, but if that mobile missile launcher was operated as I believe it was in this case "In Local" control then no such target identification would have been possible all the operator would have seen would have been a blip on his radar with no further information. He fired thinking that this was a Ukrainian Military Transport.