That is the conclusion of a study by a Yale economics professor who estimates that travelers are losing out on more than $6 billion in savings a year because of the limits to shopping. In addition, the study says the restrictions have prompted up to 41 million passengers per year to forgo air travel.
"At a time when independent, transparent comparison shopping is most needed, some airlines are attempting to restrict access to their fare and schedule information," said the report by Fiona Scott Morton, an economics professor at the Yale School of Management. She conducted the study for the Travel Technology Assn., a group that represents several travel websites.
The study said Delta removed its fares from about two dozen travel and metasearch sites since late 2010, including TripAdvisor.com, CheapAir.com, Vegas.com, AirGorilla.com and Fly.com. The study said American Airlines and United Airlines have also reduced distribution of their fares on travel websites in recent years.
Delta and several other airlines defended their right to choose where they display their fares and say travelers can still find many websites that let them comparison shop.
"Delta reserves the right to determine who it does business with and where and how its content is displayed," the airline said in a statement. "Delta will continue partnering with a limited, but responsive and adaptable group of online retailers who we believe effectively support our efforts to provide a robust shopping experience."