What is the best or most diplomatic way to get someone to say “yes” when you ask them to swap seats on an airplane?
Often people wind up in this situation because they’ve booked late and there were only individual seats scattered around. If you have 2 middle seats, it’s going to be hard to trade that for an aisle or window, because people don’t usually want to give up an aisle or window to be stuck in the middle.
People are generally nice and will gladly trade like-for-like if they are traveling alone. So if you have an aisle and a middle or two aisle seats, you’ve got a good chance at doing the swap.
Be ready to accept a ‘no” for no reason. If it’s really important, offer money and help them move their carry-on. As a frequent flyer (typically 2-3 times a month) I’ve both accepted and denied requests depending on the situation. Therefore, make the situation as pleasant as possible and avoid confrontation at all costs. Solicit help from a flight attendant, preferably before boarding the plane to explain you special requirements.
Do also consider that some people may have their own reasons for not wanting to swap, and so long as they are reasonable and considerate, it’s better to accept and maintain a good standing with your nearby passenger to at least have a slightly more pleasant flight, as opposed to an invisible animosity toward each other.
If you can manage to intercept someone and ask to exchange seats before they have actually sat down in them, stowed away their items, fastened their seatbelt and began to read the in-flight magazine, you have a much better chance of getting them to comply.
And to re-iterate, if one of you can exchange a middle seat for a window/aisle, do so, as regardless of whether or not someone has a preference, nobody likes to be stuck in the middle of two strangers.
If they say no, say “That’s no problem, I thank you anyway” and ask someone else. Then let them reflect on their decision throughout the flight. Better this way than get visibly annoyed with them and endure the awkwardness for the rest of the flight. It’s not their fault you didn’t check-in or book together etc.
If all else fails, ask the cabin crew if there are any vacant sets of seats once all passengers are seated. Usually they will attempt to accommodate you if they can.