All I know is the "Check Six" function in the game in damn worthless half the time. Use it when someone is getting run down and they obviously don't see the attacker, not when they're in a turnfight and you're checking them for someone on their 2 o'clock. They're going to have to break off their turn to defense against a non-existent enemy and you probably just got them killed or prevented them from attacking their target.
When the air is thick with aircraft, get a microphone and do a quick voice check. In this situation the built-in Check Six does more harm than good... unless you were intentionally trying to get someone to break off so you could get the kill instead.
Yesterday I got check-six'd for an LA7 that I was 200 yards behind and in a turn-fight with in my Zero. That was just carelessness, not even checking the relative distances between the friendly and the target or what was going on between them. There was no other aircraft nearby. I obviously saw the LA... I didn't need a check six in that situation... if you're not sure use voice.
If you can't use voice because you're a mute or you have throat cancer or you don't have a microphone or your stereo is blasting Billy Ray so loud your ears are bleeding, accept that fact that you can't save everyone and sending a check six when you don't know the situation yourself might do more harm than good

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