Trip Advisor, the online travel site, is pretty much worthless now for people who fly out of airports that serve as Delta hubs, such as Minneapolis St. Paul.

The airline no longer exists on the site.

Delta has refused to allow Trip Advisor any access to its fare information, making it impossible to find lower fares as airlines force passengers to shop on their own websites.

And why wouldn’t they? Check the images above for the fares for a flight later this month from MSP to Los Angeles on the TripAdvisor site.

Now compare to the same route on Delta’s website.

“Delta reserves the right to determine who it does business with and where and how its content is displayed,” a company statement said.

But passenger advocates say this is what happens when the government stands by and watches the airline industry consolidate into just a few airlines, some experts tell the New York Times today.

“Where a significant portion of Delta’s profits come from is ancillaries after you buy the basic transportation,” said Max Rayner, a partner at Hudson Crossing, a travel industry consulting company. “That’s one big reason for Delta to be hellbent on denying access.”

The manager of TripAdvisor says you’ll pay more.

“Imagine a world where you have to download six or seven apps just to book a flight,” he tells the Times. “It’s already hard enough.”

The airlines make flying miserable, and then charge you fees to make it less miserable.

A Yale School of Management report, prepared for the trade group Travel Technology Association, says travelers will pay $6 billion more if the airline assault on travel sites succeeds.

“Restrictions by airlines of broad access to airline information—prices and schedules—substantially reduce consumer welfare. This study estimates the potential reduction in net consumer welfare of limiting airline price and schedule information to only airline websites could exceed $6 billion per year.”