Comment by adastra22

I don't watch those kinds of movies. I have, on the other hand, worked for a large aerospace firm supplying these weapon systems.

A transponder is how civilian planes tell exactly where they are relative to each other. Missiles use IR, radar-bounce, and other methods for the last-mile delivery of explode-y bits, but when launched from afar (e.g. a surface-to-air missile launched from land towards something over the horizon) they need to be pre-loaded with the exact position of the target, as they need to get close to it before switching to a homing mechanism. If the target has a radio transponder, that makes this step trivially easy.

If Venezuela wanted to shoot one of these planes down, with the transponder off the missile is as likely to lock on to a commercial airliner. They're not going to take that risk.