Despite the plunge in fuel costs, domestic airfares for the year have changed little from 2014.
According to Farecompare.com, a site that tracks ticket prices, the cheapest domestic airfare rose by 1.5% in 2015 over 2014. The U.S. Department of Transportation has yet to calculate airfares for the entire year, but the average domestic fare for the first six months was $388, down less than 1% from the same period in 2014.
As long as demand for air travel remains strong, airlines are not under pressure to slash fares, said Seth Kaplan, managing partner for the trade publication Airlines Weekly.
"These business are not charities, and they are not going to give consumers benefits just for the sake of doing it," he said.
Because of a series of mergers over the past decade, more than 70% of all domestic traffic is now controlled by four airlines, said Richard Gritta, a University of Portland finance professor and airline expert. The big four carriers — Southwest, American, United and Delta — controlled 50% of U.S. air traffic 10 years ago.
"Why would they want to cut fares when we don't have a choice if we want to fly?" he asked.