MINNEAPOLIS >> Delta Air Lines may have charged some frequent fliers higher fares than other customers for almost three weeks because of a computer glitch.

Delta acknowledged on Wednesday that frequent fliers who logged into its website to search for fares saw different prices than people who searched anonymously. Delta spokesman Paul Skrbec said frequent fliers sometimes saw higher fares, sometimes lower. He said the problem has been fixed and apologized to travelers. He didn’t know how many people had been affected.

The two business travelers who first noticed the problem said fares they saw were consistently higher when they logged in via their frequent flier accounts.

A few weeks ago, security company executives Patrick Smith and Steve Lisle were side-by-side with their laptops open on the same conference table at their company’s Minneapolis office, trying to book tickets on the same flight to St. Louis. Smith was logged in as a frequent flier. Lisle wasn’t. In three out of five of their tests, fares for the frequent flier were consistently higher, including a $124 price difference for a trip to Los Angeles, the two told WCCO-TV in Minneapolis, which first reported their experience on Tuesday night.

“Not just a couple of bucks. It was pretty significant,” said Smith.

WCCO also searched for three fares, and in one of those cases the frequent flier was offered a fare that was $168 higher, the station reported.

Lisle said the encounter left them wondering if they overpaid on earlier flights.

“We would have absolutely no idea. There’s no way for us to find out,” Lisle said.

Atlanta-based Delta Air Lines Inc. has been upgrading elements of its website for more than a year. An upgrade less than three weeks ago to its flight search engine caused the fare discrepancies, Skrbec said. After discovering the problem, the airline reverted to its old search engine. Skrbec said the fix was made before the TV station contacted Delta.

Airlines have long internally discussed charging more to frequent fliers with a willingness to pay, but none have put it into practice, said airline consultant Robert Mann.

“This would be the equivalent of the soft drink machine that dispenses $5 cold drinks on a sweltering hot, sunny day and $1 drinks on a cold, dreary day,” Mann said.