Once Spirit is gone, the legacy carriers will raise fares on Spirit’s former routes since they’ll no longer be forced to compete with ultra-low-cost pricing. Those higher margins will give them the financial flexibility to move into Frontier’s markets. With that additional revenue in hand, they can then aggressively compete on Frontier’s core routes—using profits from the former Spirit markets to subsidize cheap seats where Frontier operates. Ultimately, this allows the legacies to pressure Frontier from both sides: charging more where Spirit once flew, while undercutting Frontier where it still tries to compete. Frontier pilots should be hoping for some sort of Spirit miracle.