Actaea

How do air defense centers work? Where do they get their energy, and how far can they shoot? Are they controlled autonomously or from a central hub? Can we disable some element to ensure the safety of our air transport? Can we ignore it and simply avoid flying too high? Radars don't detect helicopters flying low to the ground.

They mainly consist of people armed with these things and various military equipment. Stationary installations don't require too much energy, so they are powered by local energy generators located nearby. Their weaponry is quite good thanks to supplies from the Kittypinkian general, but everything else is far behind.
You can always try to fly outside the radar range, but it's at your own risk.