On July 3, 1988, USS VINCENNES (CG 49), an AEGIS cruiser, shot down Iran Air flight 655, killing all 290 persons onboard. That aircraft had departed Bandar Abbas, a joint civilian/military airfield in Iran and was on its way to Dubai. Most of the passengers were pilgrims on their way to Mecca for the Hajj. Flight 655 flew this route twice a week, along the standard civilian air corridor.
At the time of the surface to air engagement, VINCENNES was actively engaging several Iranian fast patrol boats operated by the Iranian Pasderan Revolutionary Guards. CO VINCENNES had earlier decided to engage the boats with his 5" guns after the boats apparently began firing at his embarked SH-60B LAMPS helicopter then flying nearby. The combat information center in VINCENNES was VERY busy during this period. Many mistakes were made by VINCENNES personnel that led up to the firing of two STANDARD missiles.
Subsequent to the shootdown, many operational procedures were changed to improve situational awareness and extensive training was conducted Fleet wide to lessen the chances of this happening again.
This incident occured at the height of the Iran-Iraq war, when ships were being regularly attacked in the Persian Gulf by both sides.
One year before, USS STARK (FFG 37) had been attacked by an Iraqi Mirage F-1EQ5 fighter-bomber with two French made AM-39 Exocet anti-ship missiles. Thirty seven American sailors were killed in that attack. The CO of STARK was subsequently relieved for cause for not having his ship in the proper state of combat readiness in a known combat zone. The Rules of Engagement then in effect at that time were also found to be ambiguous and were changed. The word went out that we would NOT suffer the first blow again.
(At the time of both incidents, I was a Navy surface warfare officer on active duty.)
There's a LOT more if you want it...but it can be a long read.