"We are more bullish on airlines today than we've been in a long while," said Conor Cunningham, an analyst with Melius Research. Reduced capacity has also made airlines less fussed about aircraft delivery delays. Southwest last week said its reduced growth over the next three years has left the company with surplus planes. As a result, the Dallas-based carrier is planning to sell its planes in the secondary market. Similarly, Frontier has deferred taking deliveries of 54 Airbus jets. JetBlue has deferred deliveries of 44 new jets from Airbus. "Every aircraft must continue to earn its way into the network," JetBlue President Martin George said. Encouragingly, there is broad consensus among carriers over capacity discipline. Even ultra-low-cost airlines, which have traditionally relied on high growth to fully utilize their fleets and lower operating costs, have tamped down their growth plans.