How to sit together when you booked separately

Yes, you can sit together even though you booked separately — but it will not happen by itself. The reliable route is to call the airline once both tickets exist and ask them to link (some airlines say "cross-reference" or "associate") the two reservations, then choose adjacent seats on the seat map. Linking tells the airline's system you are travelling as a party, which also helps if a flight is delayed or your booking has to be rerouted.

Do it in this order

1. Book. Do not wait — an empty pair of seats is worth nothing if the fare disappears while you deliberate.
2. Open the seat map for your own booking straight away and look at what is left. Pairs go early, especially on short-haul.
3. Call the airline with both confirmation codes to hand and ask them to link the bookings. Most agents do this in under a minute at no charge.
4. Once linked, ask the agent to seat you together in the same call. It is usually easier than doing it yourself online, because the agent can see both records at once.
5. Check in at exactly the 24-hour mark. Airlines release blocked and unassigned seats then, and this is often the best chance to move next to each other.

What to do if there are no adjacent seats

Take any two seats in the same cabin first — never leave yourself unseated. Then re-check the seat map every day or two. Seat maps change constantly as people cancel, upgrade or get moved for operational reasons. If you are still apart at the airport, ask at the check-in desk, and if that fails, at the gate: gate agents control the final seat assignments and often have spare inventory.

Asking another passenger to swap on board works more often than people expect, but only if the swap is like-for-like. Nobody will trade an aisle for a middle seat, so offer the better seat of your pair.

Fare types matter more than politeness

• Basic economy: seats are assigned at check-in and often cannot be chosen at all, even for a fee. Two basic economy tickets are the worst case for sitting together.
• Standard economy: standard seats are usually free to pick; extra-legroom and forward rows cost extra.
• Southwest: a special case — see the Southwest guide.
• Travelling with children under a certain age: US carriers are required to make a reasonable effort to seat a young child adjacent to an accompanying adult at no extra charge. Say so explicitly when you call.

Before any of this, make sure you are on the same flight

All of the above assumes the two bookings are for the same flight number on the same date. If you have not booked yet, start with how to book the same flight as someone else.