The clear sky achievement requires (and I'm recalling this from memory) %50 of aircraft destroyed and a minimum of 30 aircraft destroyed. I have shot down in countless battles 45-50 aircraft and still haven't received the achievement. typically the enemy aircraft carrier has 35-50 planes, so why am I not cracking the seal on the achievement? even if I factor in all the spotter planes and catapult launched fighters with a swag the total number of potential aircraft on the enemies team might be 75-80 aircraft. Unless I'm way off on how many aircraft could be on an enemies team, it appears to be broken to me, because 45-50 aircraft meets the %50 requirement and the minimum requirement.
The signal for clear skies is pretty useful and one of the first signals I deplete, so if someone could tell me what I'm missing here I'd be grateful.