Delta Air Lines said a glitch that appeared to show different airfares to frequent fliers happened because it was trying out a new company to power flight searches on its website.
The airline has taken heat from customers after reports that people who logged into its website with their frequent flier number were offered higher fares than those who searched anonymously. Frequent fliers are an airline's most-valued customers, and the idea that they were asked to pay more has rankled travelers.
Late Friday afternoon, the Transportation Department said it is "looking into the Delta pricing issue." Spokesman Bill Mosley refused to elaborate.
The airline offered is first detailed explanation of what went wrong in an interview with The Associated Press Friday.
Delta and other airlines use third-party companies such as Google's ITA Software to deliver results when customers search for flights. Those search providers sift through all the available seats, possible connecting flights and different fares to show flight options to customers.
Delta was thinking about switching search providers, so starting on April 20 it ran a side-by-side experiment, Bob Kupbens, the airline's head of e-commerce told The Associated Press. People who logged in with their frequent flier number saw results from the airline's current search provider. People who searched anonymously got results from the experimental provider. Delta declined to name either company.
"We don't want to take all of our best customers, who we care the most about, and put them immediately onto a new search engine," Kupbens said. Ultimately, he said, the airline hoped the switch in search companies would provide travelers with faster and more-relevant search results.
The problem was that one of the search engines included flight possibilities that the other one didn't, Kupbens said.
For example, one search might include a cheaper flight with a less-desirable connection, while the other one didn't include that option. A customer would see that one result had cheaper options than the other.
Kupbens said the airline never sold customers the same exact roundtrip flights at different prices.
"To be clear, we never _ and couldn't have, based on the technology _ we never sold the exact same itinerary for a different price. So what customers were seeing was a difference in search results, not a different price for the same itinerary," he said.
Delta ended the side-by-side test on May 9.
Kupbens said the problem was not with the experimental search provider, but with the way Delta asked it to assemble its results. The new search provider is still being considered for a switch, he said.
The airline industry has long been criticized by customers for a lack of transparency in its pricing. Airfares change from hour to hour and it's often not clear how many seats are left for sale on a specific flight.
This latest snafu just feeds into customers' fears that they aren't always getting the best price.
"When it comes to prices, it's time for airlines to start telling the whole truth," Charlie Leocha, director of the Consumer Travel Alliance said in a statement. His group and the Business Travel Coalition on Friday called for the Department of Transportation to review price-display practices for airfares and the growing number of fees for services such as checked baggage and seat assignments.
Shares of Atlanta-based Delta Air Lines Inc. closed down 28 cents, or 2.7 percent, at $10.13.
Mayerowitz, who reported from New York, can be reached at http://twitter.com/GlobeTrotScott.