-1, that would be too easy for cv's to get spotted from coastal airfields. Just one upper comes out of a field in the sector and the cv gets lit up like a Christmas tree.
I'd rather see a system where you can post icons on the map indicating enemy forces (e.g., cv's, bomb raids, fighter attacks, etc.) but this has potential to get abused.
Edit: to guard against icon spamming, a player can only make one mark every 15 minutes. Also, the player has to be within 6k of the enemy to make the respective icon mark to prevent wild goose chases