[scottdevries]

I don’t have first-hand knowledge of how an anti-aircraft system works, but my theory is that the attack was partly automated. Keep in mind that the plane was delayed by about an hour on the tarmac, so that may be a factor.

If the plane was cleared for take-off, this would have been coordinated with the defense forces, who would’ve been prepared for a civilian plane leaving Tehran. This was probably sent via a take-off window, so the plane being delayed on the tarmac missed the window.

Keep in mind also that the US had scrambled fighters from the UAE, and so there was a possibility of intrusion on Iranian airspace. So, a delayed plane outside of the take-off window may have looked like a radar-dodging fighter to an automated anti-aircraft system.

[kitsuac]

I'm in a similar boat, being rather uneducated here. But I thought it wasn't completely unusual for countries to prod each other's air space. It seems really dangerous for Iran to just auto fire at an encroaching aircraft, potentially starting off a war. In that sense it may be lucky it wasn't a US fighter.

[antpls]

Same boat here. I thought commercial flights had easily recognizable radar signatures, different from drones, fighters or cruise missiles.

Even for an automatic detection system, this should be easy to detect as "non immediate threat"

[mytailorisrich]

Apparently not so easily recognizable considering that the Russians shot down a Korean Air flight in 1983, the Americans shot down an Iranian flight in 1988, MH17, and now this.