Originally Posted by RandomBaritone

There's an unsubstantiated belief that the legacy carriers may raise online prices for a specific passenger when they have reason to believe that person has searched for the same fare before.

Let's say, for example, you've regularly searched BOS<>SFO, seen prices in the $500 range, and chosen not to buy -- perhaps in the hope that prices would drop. The thinking is that the carrier would note that search in your browser cookie and ensure that the next price you saw was higher, presumably in order to instill a sense of urgency in case the price should climb yet again.

Some on FT have "confirmed" this behavior by logging out, deleting cookies, and then attempting to buy the same tickets, whereupon they've seen lower fares. But of course this is the very definition of the post hoc fallacy. Fares change all the time, often by the minute.

To my knowledge no carrier has acknowledged taking part in such schemes. Though they wouldn't be illegal, they would be pointedly penalizing their best customers to no real advantage.