Flight 752: How easy to target a civil plane as hostile?

Tehran, Iran - The Iranian government has admitted that UIA Boeing 737-800 was shot down by an anti-aircraft missile.

On Jan. 8, the Ukranian International Airlines Flight PS752 crashed shortly after Iran hit the American bases in Iraq with ballistic missiles, a period when the Iranian Air Defense forces could be on high-alert status.

The aircraft was presumably identified as a hostile aircraft by Iran's air defense systems.

Soon after the crash, western intelligence services stated their doubts that the aircraft had been shot by a missile, although Iran was quick to claim it was a technical failure.

As a result, all 176 people aboard were killed as a result of terrible mistake. Most of the victims were Iranian citizens (82), followed by Canada (63) and Ukraine (11). The profile of victims requires a further analysis to determine if it was really a mistake as it is said.

How easy to mix a civil passenger plane with a hostile military aircraft before firing a missile?

The principle of air defense is to detect hostile aircraft through early warning systems such as radars and destroy them via SAMs (Surface to Air Missile) or Fighter Jets. But there are several steps before identifying an aircraft as hostile. This process is called, detection, identification, interception and destruction (if hostile act observed) in NATO.

The first criterion for identification is the location, where the aircraft appeared on the radar screens first. If it's within the defender's airspace, the plane is most probably friendly. Flight 757 took off from Tehran Imam Khomeini International Airport. Iran defense units wouldn't miss that.

The second step is to check the squawk of the plane. All civil planes, including military planes, have transponders. A transponder is an electronic device that produces a response when it receives a radio-frequency interrogation from ground units, which are responsible for the management and control of the designated airspace within a specific area. It allows those ground units to identify the aircraft from its squawk as friend or foe.

If the aircraft transmits previously assigned transponder codes, it must initially be assumed as friendly. Civil commercial planes are identified via transponder codes called Mode Charlie while military planes are equipped with a different transponder called Mode 2.

In the case of flight UIA Flight 752, the aircraft should have been transmitting a Mode C code since it was a civil passenger aircraft.

Another criterion is the behavior of the aircraft. If the aircraft leaves the route stated its flight plan and flies towards a strategic target, it should be warned by ground units to force the plane to stick its route. If no positive answer received, interceptor jets should be scrambled to escort the aircraft to see if there is a problem.

Another sign to be identified as a hostile air vehicle is flying at low altitude without squawking. In this case, the aircraft only appears on military radar screens as a raw echo.

This scenario doesn't seem relevant either as Flight 752 was a civil plane and took off from a civil airport after all checks done under the guidance of a civil air traffic unit.

We don't know which circumstances triggered a missile defense operation against a civil plane, but it shouldn't be that easy even for unruly countries like Iran.

Also read: UIA Flight 752 is the fifth airliner that has been shot down since 1983

The article was written by a former NATO officer for Airlinerwatch, who wants to stay anonymous