

To the best of my knowledge the ads-b transponders operate with the same interface as previous transponders. That is they can be active, stand by or off. Commercial airliners should never turn them off in the air, but they do have the ability to.
For military aircraft this requirement is almost certainly only going to apply when in “friendly airspace” and at altitudes with commercial traffic. Especially when not on an operational mission.
For truly secretive missions they will likely get blanket clearances in friendly airspace to travel at specific altitudes so they can travel transponder off while avoiding the commercial traffic.
But I’m not an expert by any means.




That’s a tough one. But if they’re going to operate in a way where they don’t want Venezuelan authorities to know they’re there (I got the impression they were making a show of force so…) they do need to inform the atc of friendly countries operating nearby so they can ensure flight plans keep them apart.
But, I don’t know what (if any) procedures they have for this kind of thing. But to me it makes sense, you either close the nearby airspace (kinda makes it obvious something is going on), inform friendly atc so they can keep squawking and non squawking traffic apart. Neither just makes aviation extremely dangerous.