Booking seats together on your next flight isn’t necessarily the best choice.

When you book a flight you usually have the option to select your seats. If two people are traveling together, the default option seems to be selecting two seats beside each other. This may not be the best choice.

If a row of three is open (and there’s no extra charge for seat assignments or the charge is the same) consider choosing a window and an aisle seat, leaving the middle open.

If the plane isn’t full, a middle is the most likely seat to remain empty, especially at the front of the plane, where extra legroom usually costs more, and at the very back of the aircraft, which is usually the last to be filled. Leaving an empty middle between two people increases the likelihood that those two passengers get extra room free; that is, an empty middle seat to share.

If the plane is full and someone is seated in the middle seat between you, then trade them an aisle or window. Trust me; almost anyone will take that deal. (I’ve seen some people offer to sell that better seat for a modest amount (!) or say, “Buy me a drink on board and you can have my aisle seat instead of your middle.”)

(Apparently) little known fact: On most airlines, you can also buy the extra empty seat. (For example, when I found a great mistake fare on a flight to Japan, I bought a row of four for less than the usual price for one seat. Husband and I took turns stretching out for a nap on the long flight.)

You could also choose two aisle seats across from each other. You’re still sitting together (that is, with no passengers in between you), and you’re guaranteed a little more breathing space.

If you don’t like the seats that are available that you can assign yourself, you can set a free email alert for a better seat.

How do you know which seat is best? While I’ve been using SeatGuru for years, I don’t find it nearly as useful as it once was and have since found a better source for airline seat maps.

“LOPA” refers to Layout of Passenger Accommodations. It doesn’t just show seats; it’s a detailed schematic of the passenger cabin that’s drawn to scale. Here’s a site that shows these for a number of airlines, both foreign and domestic: aeroLOPA.

What can you see? Lots, including details of how each seat is angled, bulkhead and bassinet placements, larger or handicap-accessible lavatories, and even where windows are located relative to seats (no more picking seats where the windows are misaligned and you can’t easily see out). Not only do you get a seat’s legroom and width, you can also find out which brand and model seats are installed.

For example, here’s the front business cabin of a United Boeing 787-9 with Polaris seats installed. It shows how the seats angle and which middle seats are close to each other.

Twist’s Take: Booking seats together on your next flight isn’t necessarily the best choice.