[adastra22]

I was speaking perhaps too casually, but "military things" was meant to mean offensive operations. The kind of things where you might expect to be fired upon (or at least need to take precautions against that happening). A transponder is a homing beacon for missiles.

[isodev]

You watch too many movies, there are plenty of other things for the missiles to track. Transponder in civilian airspace is just how you keep planes from crashing into each other.

[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.