[lvlrsSTI]

The Bell helicopter was bought by Iran in 1979. Its 45 years old. Because of Western sanctions, the aircraft could not be maintained to modern safety standards. The avionics are also nearly half a century old, unlike modern avionics that can fly aircraft purely by instrument (all pilots undergo fly by instrument training ie, they only look at the instruments to fly & land), the ill-fated helicopter was likely flown by pilot visibility through bad weather over the mountain range. Under normal circumstances, the flight would have been denied due to very poor visibility. But that these were VIPs on tight schedule.

 Bad visibility? How come the other two helicopters reached destination without problems?