Question:
During the initial phase when phasing and non-phasing players fly their CAP missions, who flies first?

Answer:
Here’s how it works (text taken from WitD 16D):
One player, the initiating player, announces that he is initiating a specific air operation. Should both sides wish to initiate an air operation at the same time, the phasing player first initiates an air operation, and, when that operation is over, the non-phasing player then may initiate an air operation (he may decide not to do so – for example, the outcome of the phasing player’s air operation may have removed the reason for the nonphasing player to initiate an air operation). Continue to alternate air operations between the two sides until both sides no longer wish to initiate air operations at the same time.

Source:
TEM 59/60