The U.S. Justice Department opens an investigation of the largest airlines, Delta, American, United Continental, and Southwest for collusion in limiting expansion. The major 4 airlines control 80% of the domestic airline seats in the U.S. The 3 major airlines have grown slowly compared to Southwest in recent years. JetBlue and Spirit are also growing faster. Southwest plans to expand by 7% in the 4th quarter. U.S. airline domestic seats show slow growth since 2010, with growth picking up in 2015 over the prior year to 3.5% in 2015, according to Innovata. For 2013 and 2014 <0.5% growth in seats, in 2012 decline of <1%, 2011 growth of less than 1%, and slight decline in 2010. During the crisis 2008-2009 airlines cut seat capacity. Price increases have averaged 5% increase from 2007 to 2014 to $391, adjusted for inflation for domestic seats. The U.S. Justice Department investigation will look at "possible unlawful coordination."