That's exactly what it says in the article. There's even a little bit more info in there.

Not exactly click bait when presenting facts.

Context matters though. You defend your territorial integrity or you lose that space as a means of protection during the event you actually are attacked.

Korea would be in violation of international laws should they shoot down one of these planes. They can engage them and escort them out.

These days it does seem considerably more risky to fly through Russia and China's air defense zones. The Chinese are furious with America's navy for basically doing the same thing but in the ocean.

How is it click bait? It is a factual statement.

If someone doesn't know (gee what a loser) what an air defense zone is, that's their problem-- not Reuters'.