The return-flight trap: why round-trip fares aren't always cheaper
Somewhere in the 1990s it became common knowledge that round trips are cheaper than one-ways, and like a lot of common knowledge about flying, it fossilised while the industry moved on. On the routes I search most, booking out and back as a single return is now frequently the more expensive option — and occasionally by a lot.
Why the discount existed, and why it died
Legacy airlines priced one-ways punitively on purpose: business travellers needed flexibility, so a one-way ticket cost nearly as much as a return, and the "round-trip discount" was really a one-way penalty. Low-cost carriers blew that model up. Ryanair, easyJet, Vueling, Wizz — their return fare is literally two one-way fares added together. There is no discount to capture. And once half the market priced that way, one-way penalties started eroding on the legacy side too, at least in economy on short-haul.
What booking a return actually costs you
If a return is just two one-ways in a trench coat, booking it as one ticket costs you the thing that matters most: the freedom to pick each direction independently. Concretely:
You're locked to one airline both ways. On London to Marrakesh, the cheapest outbound day might be Ryanair from Stansted and the cheapest return easyJet into Gatwick. A round-trip search on either airline's site can't see that combination — it can only show you Ryanair both ways or easyJet both ways, and you pay whatever the worse direction costs.
Cheap days don't line up. Outbound and return demand have different shapes — holidaymakers fly out Friday and back Sunday, so those days are expensive in one direction and cheap in the other. Two one-ways let you take Tuesday out and Saturday back and collect both cheap buckets. This is the same weekday mechanics I covered in reading a price calendar, applied twice.
When the return still wins
Fairness section, because the trap runs both ways. On long-haul, legacy one-way fares are still often brutal — transatlantic one-ways can genuinely cost 70% of the return, and there mixing tickets is usually a mistake. Some full-service short-haul fares still bundle a small return discount. And a single ticket has operational value: if the airline cancels your outbound, your return survives untouched, whereas two separate tickets mean two separate problems. On a €35-each-way hop like Barcelona to Madrid, a €5 saving from mixing isn't worth the coordination overhead. The mix-and-match play earns its keep when the gap is €30+, which on low-cost routes it very often is.
The practical rule
Price every trip both ways before booking. It takes one extra search — or none, if the tool does it for you. Flight Combinator treats every trip as two independent one-way legs by construction and shows the cheapest airline for each direction, which is the whole thesis of how we search compressed into a data model. The return fare isn't sacred. It's just a bundle, and bundles are only ever priced in the seller's favour on average.