Some airlines use nonstandard widths and configurations. The best setups have no middle seats. Seat strategy You can put up with even the worst airline seating if you're next to an empty seat. Middle seats in the center section are considered the least desirable, so they're the last to be assigned. If most of the seats on a plane are in groups of three, one member of a couple will almost always be assigned to a middle seat.
Couples can ask for an aisle and a window seat in a three-seat row.
There's a good chance that the middle seat won't be assigned. Those lines say they assign middle seats in those sections only when planes are full. If you're a very-frequent flier, that's big advantage. But if you're not, your odds of being in a middle seat or next to an occupied middle seat increase. Certain seats have extra space, even on planes with the most limited legroom.