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MIAMI (CBSMiami) – If you shop online for flights, chances are you visit multiple sites in search of the best deal.

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On average, people questioned said they check three sites before ultimately buying a ticket.

But that may soon change as more airlines are limiting the number of third party comparison sites they’ll allow to quote their price.

Southwest has long sold its fares exclusively on its own website.

Lufthansa recently announced it will start charging $18 more for tickets sold on comparison sites.

Click here to watch Lauren Pastrana’s report. 

And last year, Delta pulled its information from several sites, arguing they don’t have permission to use Delta’s data at all.

“The comparison shopping experience is going to get worse as more big airlines restrict information,” Dr. Fiona Scott Morton of Yale University said.

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Scott Morton believes that means consumers will ultimately pay more.

“So it’s in the interest of the airlines to make these searches difficult to do,” she explained.

Scott Morton said online shoppers suffer search fatigue: the more sites they’re forced to visit, the more likely they are to settle for a more expensive price.

Travel researcher Douglas Quinby say the websites will take a hit if the changes become a reality.

“It’s a big deal for some of these small sites,” he said. “I think we may start to see over the next few years more airlines pull some of their content or be more assertive about how their content is displayed.”

Quinby said Delta’s move may set an important precedent that airlines own access to their fare and schedule information and can control who displays it.

Airlines make the most money when they can funnel people back to their own sites to push add-ons and upgrades.

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A New York Times report published last week said Delta made $50 million last quarter just by selling these extras.

Lauren Pastrana