The main suspicions are that the Ukrainian passenger aircraft was downed by a Russian-made Tor-M1 missile. The Tor is among the most modern air defence systems Iran has.
After initially denying responsibility, Tehran has admitted that Ukraine International Airlines flight PS-752 crashed as a result of “human error” when it was misidentified as a cruise missile killing all 176 persons onboard.
Iran on Saturday admitted downing the jet “unintentionally”, three days after the crash.
Ukraine International Airlines flight PS752, en route to Kyiv, was shot down on Wednesday near Imam Khomeini Airport in Tehran shortly after take-off, and only hours after Iran had fired missiles at two air bases housing US forces in Iraq.
The Tor, also called the SA-15 Gauntlet by NATO, is a short-range “point defence” system that integrates the missile launcher and radar into a single tracked vehicle.
It is designed to be mobile and lethal against targets at altitudes up to 6,000 meters (20,000 feet) and at ranges of 12 km (7.5 miles), according to the Federation of American Scientists, which researches and analyses “catastrophic threats to national and international security”.
Military aircraft and cruise missiles – which the Tor system is designed to destroy – typically plot their courses to avoid being spotted on radar. They are equipped with systems such as chaff, which confuses radar, and flares, which act as decoys for heat-seeking missiles.
To attack a target, the Tor operator must identify it on the radar screen and direct the missile to launch.
Tor missiles are guided by radar and fly at almost three times the speed of sound. That means that if launched at a target 5 km (3 miles) away, they will arrive within about five seconds.
They have a small warhead – about 15 kg (33 lb) of high explosive – but are designed to spray fragments of shredded metal, like bullets, into a target upon detonation.