"The airlines are at the same time highly intelligent (they use sophisticated pricing models! there's a reason behind every price you see!) and extremely stupid (tracking user searches is way too complicated! any price changes are just a coincidence!)."
The pricing models are sophisticated. What they aren't is
personalized. If you'd like to argue that airlines are going to raise the prices for
everybody because
one person happened to repeat a search, fine -- but keeping in mind how many users they'd have doing searches at the same time, you'd pretty much always have somebody doing a search.
There's no contradiction here.