That's kind of a political question. Politicians set the rules of engagement, which dictate the level of confirmation required before employing weapons. It's a spectrum. At one end of the spectrum a certain area can be designated as a free-fire zone in which any airborne contact is assumed to be hostile. In the middle of the spectrum it may be required to use data links and IFF to avoid firing on friendly or neutral aircraft. And at the other end of the spectrum, visual confirmation may be required.