What does this red airplane sign stand for?

[Puffin_]

[white_killer_shark_123]

Area with enemy airplane from normal ship and not CV 

[Oberendgegner]

I guess it indicates the nearby fighter squadron zone, which you are entering.

Distance on the icon (4.3km) is different to the fighters (3.9km) distance, because the fighter squadron is currently not in the exact center of the zone (see minimap).

[SkrintX]

 

7 minutes ago, GudmundurG said:

It means, AA support if it's ally and Spotted untill it disappears if it's enemy.

And if you are CV, avoid the Red plane zone.