Salute!
As Mozella advocates," the fog of war" was the most likely environment, and if the missile crew was just changing the guard, they also could have been doing a basic system check/calibration with a failed safety interlock. An alert could have been passed down from on high, but only the Iranians can address that part of the "fog". The missile battery was a highly mobile system, and the comm might have been poor, as well.
All here should realize that I am trying to "explain" things from a military point of view and not making an excuse for the terrible incident.
Lastly, the IFF is used primiarily before launch, and even the U.S. Stinger launcher has had IFF since the early 80's. Once that thing is launched, you cannot make it go blind. The really long range missiles and the command guided ones can be made to go blind or steered away from a target if the target is deemed friendly. The British debrief I got after the Falklands pointed out they could stop tracking easily and keep the Rapier missile from hitting a friendly ship or aircraft.
Gums sends...
Last edited by gums; 13th Jan 2020 at 18:44.
Reason: correction