Most people book round-trip flights at the same time because it feels responsible. You get a slightly lower fare, a tidy itinerary, and the mild comfort of knowing when you’re coming home. What you also get is a hard wall around a trip that hasn’t happened yet.
The case for booking your outbound flight first and leaving the return open is strongest on trips of a week or longer, particularly if you’re moving between cities or countries rather than planting yourself in one place. Flexible return tickets cost more upfront - sometimes significantly more - but that’s a different calculation than it first appears.
What You’re Actually Paying For
The price gap between a fixed return and an open-jaw or flexible fare varies a lot by route and airline, but on many European and Southeast Asian routes, one-way fares booked separately are not dramatically more expensive than the return leg of a round-trip. Low-cost carriers in particular price legs independently anyway, so the psychological barrier to booking separately is bigger than the actual cost barrier.
What changes when you don’t have a fixed return date is how you make decisions on the ground. If a place surprises you, you stay longer. If it doesn’t, you leave early. These aren’t luxury problems - they’re the basic conditions under which a trip becomes something you actually remember.
The Practical Middle Ground
If fully open-ended travel isn’t realistic - and for most people with jobs and fixed commitments, it isn’t - there’s a workable compromise: book your outbound flight and your return flight, but delay the return booking by a few days after you land. Even 72 hours of actual experience in a destination will tell you more about how long you want to be there than any amount of advance planning.
The key is not booking a return in the first hour of excitement when you’ve just found cheap outbound fares. That’s the moment your future self gets stuck in a city they’ve grown tired of, or pulled out of one they weren’t finished with.
One Hard Rule
Never book a non-refundable, non-changeable return on a trip where your final destination is different from your first. If you’re ending in a different city than you started, one-way fares for both legs is the only logical structure - round-trip pricing doesn’t apply and you’ll pay for the privilege of pretending it does.