When it comes to relationship minefields, watch out for frequent flier miles.
Airline status can seriously test a romance, as lovers suddenly find themselves divided into elites or non-elites -- with access to either lots of perks or just no-frills transportation.
If you're the globetrotting spouse who gets an unexpected upgrade, should you keep it, offer it to your less-traveled mate stuck in coach, or just give it up all together?
Technically, there's no "you have to," said Lizzie Post, etiquette expert, author and spokeswoman for the Emily Post Institute.
"There's nothing that says if the man gets it he should give it to his wife, or if the partner who travels more gets it they should give it to the one who doesn't," Post said.
Still, the person with the upgrade should consider what would be the best for his or her mate, she advised. But just because the frequent flier doesn't offer up the upgrade, or winds up taking it, doesn't suggest he or she is out of line or rude or not chivalrous, Post said.
It's a dilemma that can provoke strong feelings on both sides.
"This sort of almost falls into the category of babies on planes. It just stirs the pot," said Gary Leff, a frequent flier who shares strategies for making the most of traveler loyalty programs on his blog, View from the Wing.
Take Pat Baird and Diane Pallissard, who live in Pleasant Prairie, Wisconsin, and recently became engaged.
He is the frequent flier in the relationship -- jetting off for business every week and accruing about 50,000 miles a year -- so he often gets upgrades when he travels. She does not.
That sometimes leads to "you-take-the-seat-honey-no-you-take-the-seat" kinds of arguments when they end up booking a trip together in coach and discover Baird has received a last-minute pass to the premium cabin.
'My girl should get the upgrade'
Baird, 43, feels it's only right and chivalrous to let his fiancée have the upgrade, but Pallissard, 47, cringes at the thought of taking advantage of a perk Baird has earned through lots of arduous travel.
So when Baird was upgraded on a recent flight from Munich, Germany, to Chicago, Pallissard declined his many offers to swap seats and stayed behind in economy class.
But when a similar situation came up just before a flight last month from Portland, Oregon, to Chicago, she gave in.
"I felt terribly guilty. I kept telling him, 'No, no, you're the one who has been spending so much time on airplanes lately, you take the seat,'" Pallissard said.
"Finally he insisted, so I took it, but I felt bad, because I felt like he's the one who earned it so he should be the one who has it."
Baird, on the other hand, was perfectly pleased.
"She's my girl and my girl should get the upgrade," he said. "I'm gone so much, I don't get a chance to pamper my lady. So if she can sit with (a few) more inches of legroom for four hours, then why not?"
Leaving your spouse in coach
Other fliers are apparently not so generous with their mates. When the crew on Baird's flight found out that he had given up his upgrade for his fiancée, they were floored, he said.
The flight attendants -- who were so moved by Baird's gesture that they snuck him free glasses of wine and a cookie from the premium cabin, he recalled -- told Pallissard that business travelers are often perfectly content to relax in first class while their spouses sit in coach.
"Hubby has left me in the back on several occasions," one flier posted.
"Wow, and you let him live? You must be a very generous person," another poster responded.
Jared Blank, who writes the blog Online Travel Review, recalled how he took an upgrade 10 years ago while his then-fiancée sat in coach.
"I cannot imagine why she married me after I allowed that to happen," he wrote recently. Blank made up for it during a flight last month, when he gave his wife his upgraded ticket and sat in economy with their kids.
Going for compromise
Some couples decide who gets the upgrade based on which spouse has more work to do on a flight and needs the extra room and comfort.
Still other travelers try to "split" the upgraded seat -- with one person spending half the flight in the premium cabin, then heading back to coach to let the other spouse enjoy the perk for the rest of the journey.
It doesn't always work out.
Jennifer, who used to fly more than 100,000 miles a year, was returning from Hawaii to New York with her husband two years ago when she qualified for an upgrade, but he did not. (Jennifer asked that her last name not be used for this story because she edits the Deals We Like blog and prefers to write anonymously.)
The couple decided she would take the comfy seat in business class and switch with him halfway through the flight. But he never came up to initiate the seat change and she wasn't going to volunteer, she said. As a gesture of thanks, she asked a flight attendant to send him a "massive ice cream sundae" back to coach.
"Typically, if it is a short flight I will forgo the upgrade and sit with my husband if we both cannot get upgraded," Jennifer said.
"For longer flights, I will never decline the upgrade. While I love sitting next to my husband, you just cannot beat a business class seat."
The 'Captain Kirk approach'
Leff, who flies about 100,000 miles a year, said there's definitely more pressure on the man to give up an upgraded seat to his mate. But because he and his wife put a premium on sitting together during a flight, they would rather forgo an upgrade altogether than sit apart.
"Comfort is one thing, but marriage is something else," Leff said. "I would not, under any circumstances, take the upgraded seat when she was left in coach. ... I think there is also some truth in the maxim 'happy wife, happy life.' "
But Leff also takes what he calls a "Captain Kirk" approach to the dilemma, likening it to the Kobayashi Maru training exercise on "Star Trek": a seemingly no-win situation that Kirk solved by refusing to accept the constraints of the scenario.
"I reject the premise in which one of us gets upgraded, because the only acceptable solution is for us both to be upgraded and my job is to ensure that that is the case," Leff said.
What do you do when you're faced with this situation? Let us know in the comments below.