In recent years, major U.S. airlines have seen fuel costs rise from 10 percent to as much as 40 percent of their overall operating expenses, the Los Angles Times reported. That cost, passed down to consumers, is often marked on tickets as a separate expense, enabling airlines to offer low-cost fares, while still passing fuel increases on to their customers.

"We must be able to pass commodity costs on to customers as other industries do," Robin Urbanski, a spokeswoman for United Airlines said.

Some travelers see the separated expenses as a fare hike shielded by a public relations ploy. "You can argue forever about whether this is justified, but how they are doing it shows their worst nature," Joe Brancatelli, who runs a Web site for business travelers, told the Times.