the BUK system is equipped with a civilian transponder safety lock which has to be manually disabled before a missile can be fired at an aircraft showing a civilian IFF.
And you would know this how, exactly?
References or GTFO.
Does this help . Look for IFF (Identification Friend or Foe).
IFF is active - it tells you who is a friend (and civilain != friend).
However ihtoit claims to have been trained to use the Buk, so maybe he's right.
[ the 1983 improvement for the Buk ] Additionally a non-cooperative threat classification system was installed, relying on analysis of returned radar signals to purportedly identify and clearly distinguish civilian aircraft from potential military targets in the absence of IFF.
It's not clear whether an isolated Buk TELAR vehicle has this, or whether its part of the target acquisition or fire control vehicles, and it seems the rebels were using isolated TELAR vehicles rather than full batteries.