Pre-optimizer, NYC had the highest layover costs in the system IIRC. Post-optimizer, the NYC commutable trips turned into early sign-ins with late sign-outs resulting in the current dystopian sh!tshow seen in NYC NB bid packs. The easiest way to minimize layover costs was to shunt the morning go and last flights in onto in-base lines. The company layover costs were greatly reduced by making the commuter foot the bill of those "optimizations."