"Would you change seats so I could sit by my husband?" a woman asked my friend, who had an aisle seat.

"I like my aisle," replied my friend. But a minute later, she moved to the woman's middle seat. In my friend's snap judgment, she would have been uncomfortable no matter what, either feeling guilty for remaining in relative luxury or squeezing between two large men.

She would have made the switch with no hesitation to reunite a parent and child, or if the husband or wife had appeared old or frail. Instead, my friend said, "she was just like me."

Well, almost. Where the two differ is that my obliging friend would have never asked the question. And, unless there are exceptional circumstances — or the request is for a less desirable seat — no traveler should.

I joked that my friend could have asked the woman what a swap was worth to her.

Actually, that's a fair idea. Those precious 17 inches (the width of many airplane seats) are a commodity with real monetary value as airlines pack planes and charge fees for premium spots, aisle seats among them.

Associated Press - Ap, Star Tribune
In this Sept. 23, 2013 photo, rows of slimline seats await installation onboard a Southwest Airlines 737 at the carrier's headquarters in Dallas. Southwest says passengers will have the same amount of legroom even though the new seats allow for another row onboard.

Beyond paying to sit near the front of the plane or on an aisle, many fliers book early, even forgoing deals, so they can choose a good seat. In this environment, plane etiquette calls for us to sit where assigned.

The trick is to nab a good seat assignment. It is possible. First, choose your own seats when you book. Not pleased? Return to the airline website often to see if anything better opens up. Still in Row 35, Seat B? Complete online check-in promptly, 24 hours before the flight, when new seats may be on offer. You can also arrive at the airport early and ask the gate agent politely for help.

If all else fails, take a deep breath, put on your headphones and try to enjoy your flight, even if your partner is far away. But if you're not sitting next to your child, I condone all-out begging, provided it's accompanied by an offer to buy the accommodating switcher an in-flight beverage or snack, too.