KCBS_740 SAN FRANCISCO (KCBS) — The largest airlines are changing the way they price multi-city trips, and travelers could end up paying six or seven times what they’re used to.

American Airlines, Delta, and United have all adopted the new pricing plans, but travelers who book round-trips to a single city won’t be affected – it’s likely business travelers who will feel the biggest pinch.

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“First of all, if they’re going to fly on those major legacy carriers – American, Delta, United, always compare the fare for multi-city trips with the fares for each segment if purchased separately,” Frank Werner, Finance Professor at Fordham University told KCBS.

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Werner also suggests travelers check with smaller carriers, who haven’t yet adopted the new policy.

“Book through a search engine that has the ability to book each segment separately, and from multiple airlines, so they can do the best for you, and you’re not limited to looking at just what comes back on the major airline site,” Werner said.

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Finally, Werner says anyone booking a flight online should clear their cookies before making the final purchase, which let the carrier know you’re coming back, and are more likely to buy.