Comparison sites are paid by the click

A comparison site presents itself as a neutral index of the market. Its revenue model gives it reasons to order results in ways that are not purely about price.

The business is referral, not retail

Most flight search engines do not sell the ticket. They pass the user to an airline or an agency and are paid for the referral, sometimes per click and sometimes per completed booking.

That payment differs by partner. Two identical prices from two sellers are not identical to the site, which has an incentive to surface the one that pays more.

None of this makes the displayed prices wrong. It affects ordering, prominence and which suppliers are included, which is a subtler distortion than an inaccurate number.

Not every seller is in the index

Some airlines decline to distribute through comparison sites, or distribute only part of their inventory. Their fares are simply absent rather than shown as more expensive.

This is most common with low-cost carriers, which prefer direct booking so they can sell extras themselves. A search that omits them can misrepresent an entire route.

Checking one or two airlines directly after a comparison search is therefore not redundancy. It covers a known gap in what the index contains.

The displayed price is a starting price

Ranking by price rewards the seller that strips the most out of the base. Bags, seats, payment method charges and check-in fees are added after the click.

Filters that add a cabin bag to the comparison change the order substantially, because the cheapest headline fare is frequently not the cheapest completed booking.

Hotel search behaves the same way, with taxes and property fees excluded from the sorted figure in some markets, so two listings at the same rank differ at checkout.

Cached results and the price that moves

Search results are often served from cached data rather than a live query, because live availability checks are expensive for the airline's systems to answer.

A price that changes at the point of booking is usually cache expiry rather than surveillance. Airline inventory moves continuously and the cache is a snapshot of it.

Repeating a search in a private window rarely changes the outcome, since the movement comes from the underlying inventory rather than from a record of the earlier visit.

Where these sites are genuinely strong

Their real advantage is breadth of routing. Combining two carriers that do not sell each other's flights produces itineraries no single airline site would ever display.

The trade-off is that such combinations are two contracts rather than one, so a missed connection between them is not protected. The search is worth using; the booking often is not.