User blog comment:Hayashi H/Spring 2016 Event Guide/@comment-26082413-20160519055553/@comment-26486243-20160520115457

The boss is rarely killed by one hit from the support airstrike. The vast majority of the time, it's by the combination of main fleet airstrike and support fleet airstrike. While the support fleet airstrike is unaffected by your composition or the route you take, the main fleet airstrike is greatly affected - instead of 5 squadrons most only manage to load 4 even with Akitsumaru, and the ammo penalty is 72% at best, or possibly as low as 70% due to rounding adjustments if the ammo number can't be divided by exactly 25.

Between 85.7% (6 squadrons instead of 7) malus on number of squadrons and the unavoidable 72% ammo penalty, at the STRONGEST your mainfleet airstrike using the south route will be 61.7% the strength of a north route airstrike. That would reduce my 640 main fleet airstrike hit into a 395 hit, which when combined with the 399 support airstrike, would force me to hit at least 106 in the rest of the battle on the boss, rather than allowing an instant win.