Dallas-based Southwest will begin nonstop daily service to Denver on June 4. The carrier is the fourth-busiest at Indianapolis International, with 12.1 percent of traffic in 2007. Currently it offers 17 daily nonstop departures to eight cities.
Denver-based Frontier filed for Chapter 11 reorganization on April 10, citing high jet fuel prices. It carries 4 percent of Indianapolis' 8.3 million passengers, with four daily flights between the city and Denver.