While consumers expect price drops to be reflected quickly in the price of gas at the pump, there is typically a lag with ticket prices. One reason is that airlines buy their fuel in advance, to hedge against higher costs. But if prices fall, this can effectively lock them into higher fixed prices for several months.

“If you’ve already bought and paid for your turkey for next Thanksgiving, and prices come down in the meantime, you won’t get any benefit from any subsequent reduction in turkey prices,” said John Strickland, an independent airline consultant in London. In addition, he said that airlines “also swallowed the pain of rapidly rising prices in the last year or so,” which have not been fully reflected in fares.

Image Travelers at a Delta Air Lines gate area at La Guardia Airport in New York. The airline announced on Monday that it was revamping its classes of tickets. Credit... Karsten Moran for The New York Times

Another reason is that airlines have little incentive to reduce their fares now. Many flights are full, and carriers are reinvesting much of their profit in the business, paying dividends to shareholders or giving bonuses to employees.

Airlines insist that air travel remains a bargain, even at today’s prices, once adjusted for inflation. For instance, while consumer prices have increased 35 percent since 2000, airfares have risen 22 percent, including extra bag fees and other ancillary revenue, according to Airlines for America, a trade group. Operating expenses for the nine publicly traded American passenger carriers in the first nine months of the year rose 3.1 percent as declines in fuel costs were offset by higher costs elsewhere, the group said.

United States airlines paid $115 million less in fuel costs for the first nine months of 2014 compared with last year, a 0.3 percent reduction, the group said.

John Heimlich, the trade group’s chief economist, said airlines were reinvesting at the highest rate in 13 years. This includes improvements onboard the planes, enhanced airport facilities and amenities, and rewards to employees.