This. And while lower prices tend to naturally attract customers over a higher priced alternative, you'll have a hard time convincing me that Delta drops its fares to $300 just because WN is $700. That's an enormous difference. If Delta was normally $1,000 on this route and suddenly dropped its fares to $700 (maybe $600), then sure, they might be reacting to a new market entrant. But the fact is $300-400 fares on this route are commonplace and have been for some time. AirTran was already flying this route. And those fares go up as the departure date nears, due to availability and due to advance purchase rules.