As long as your fleet has a flight deck, all fighter wings cannot die permanently. However, if a wing of fighters gets destroyed while all of your carriers are busy constructing replacement fighters, that wing is forcibly removed from the rest of the battle. If you want fighters to stay in battle until all replacements are used up, then to ensure that, you cannot have more fighters than decks in battle. This favor wings with fewer fighters, such as Gladius, Thunder, and Xyphos wings. You can field one wing per flight deck and be mostly assured that your wings will stay until they are gone. The more fighters per deck you deploy, the more likely a given wing will be forced out of battle prematurely.