Why it matters

Open-jaw means flying into one city and home from a different one — into Rome, say, and home from London — instead of returning to where you started. Airlines sell it as a “multi-city” booking, and it is a completely standard thing to do.

It matters because all three candidate arcs are linear. Every one of them ends a long way from where it began. A round-trip booking means backtracking to the start, and on a fourteen-day trip that backtrack costs a full day plus the fare or rail ticket to get there.

The options

1. Round-trip

Simpler to book, and sometimes cheaper on the airfare line alone. It is also the easier option for award travel, where multi-city routings can be awkward to price and availability is thinner.

The cost is a returned day. Fly home from Rome after a Barcelona finish and you are spending your last day getting back to Rome instead of being anywhere — and paying for that leg on top.

2. Open-jaw

Fits a linear route exactly. You end where the itinerary naturally ends and fly home from there. No backtracking, no wasted day, and one fewer intercity leg to book and endure.

The trade is a little more booking complexity, and the two legs are sometimes priced less keenly than a straightforward return. Worth checking rather than assuming either way.

My recommendation

Open-jaw, for any of the three arcs. They are all linear, so this is close to free value: it converts a wasted travel day into a real one.

The natural pairings:

• Mediterranean — into Athens, home from Barcelona or Madrid
• Northern — into Amsterdam, home from London (or the reverse)
• Split arc — into Rome, home from London

The last one is worth flagging: London and Amsterdam both have unusually heavy direct US service, which makes them good places to end a trip. Athens is the weakest finishing point in winter, since it is mostly one-stop connections — an argument for putting Athens at the start if it makes the cut at all.

What would change my mind

• Award travel constraints. If we are booking with miles, availability may simply dictate the shape.
• A large fare gap on the actual dates. Worth pricing both once dates are set rather than deciding in the abstract.
• If the route stops being linear — a two-country trip with day trips from a single base makes round-trip the obvious choice.