NEW YORK >> Don’t mess with our stretch, United Airlines, or risk the wrath of leggings lovers.

The social media matter of The Kids in Leggings vs. United snapped to the surface Sunday. That’s when one Shannon Watts said on Twitter she had witnessed a gate agent refusing to let two girls board a flight from Denver to Minneapolis because of their leggings. The girls’ dad was in shorts.

The incident, with United’s Twitter account chiming in, rolled right on through to Monday, prompting debate on whether leggings are “pants.” That especially goes for women and girls and whether the United dress code for people on standby who are availing themselves of free family passes, as this family was, has perhaps not kept pace with the elevation of stretchy pants from gym and yoga garb to more broadly acceptable.

Or are leggings more like women’s stockings and therefore not appropriate for plane travel, as one Facebook user argued — or is this a better comparison, as suggested by another: “It’s like going to a baseball game on a player’s tickets and doing something against the rules, right?”

Besides, some on social media said, many airlines adhere to the same standards for flying on this type of freebie.

“Casual attire is allowed as long as it looks neat and is in good taste for the local environment,” tweeted the United account in response to one angry leggings defender Watts whipped up Sunday.

“United shall have the right to refuse passengers who are not properly clothed via our Contract of Carriage,” another tweet from United explained.

The policy for family and friends on passes is different from that for the rest of us paying folk. For United, it seems in this case to be about the stretchy fabric.

American Airlines, for paying passengers, reserves the right to bar you if you are clothed in a manner that would “cause discomfort or offense to other passengers or are barefoot.” An American spokesman had no comment about the United flap Monday.

But American has a separate policy for employees and their guests: They’re prohibited from wearing clothes that are “torn, dirty, frayed or overly revealing.” If an employee or guest is traveling in first or business class, he or she can’t wear shorts, flip-flops or baseball caps, under that American dress code.

The point for some airline insiders, however, is different. Some of them contend anybody eligible for the types of free passage afforded the girls on Sunday is well aware of dress code restrictions, however silly they may seem from the outside.

Kristin Taylor, in tony Greenwich, Connecticut, is a leggings lover and sees them everywhere in her world. She’s also a psychologist and stay-at-home mom to two of three sons, “so no leggings for them.” She just flew in leggings to San Diego and wore a nice pair, from J.Crew, out to lunch recently with a cashmere tunic.

“Leggings are pants,” she said. “Seriously.”

Fleece-lined or paired with a fancy top for evening, leggings can be just about anything the wearer wants them to be these days, Taylor said. Besides, as the debate over leggings has gone on for years, what about jeggings? What about tights? Should Monday’s standard on “pants” rely on whether one can also comfortably perform a Downward Dog?

“And for kids? I find that ridiculous,” Taylor added. “If the father can wear shorts the girls should be able to wear leggings. If the policy was that the father had to be wearing a suit and tie and you wanted a woman to be wearing something commensurate, I would hope she would still be allowed to wear pants.”

United spokesman Jonathan Guerin weighed in Monday: “The girls (teenagers) were completely understanding. No one was upset at the gate.”

Chicago-based United regularly reminds employees about the dress rules and tells them to make sure that anyone flying with one of their passes knows the guidelines, Guerin said.

Just the day before, United had sent a memo to airport workers reminding them of the dress policy, he said. The reminder “specifically mentioned leggings, along with other no-nos for travelers using United passes, such as flip-flops and torn jeans,” he said.

He said United isn’t contemplating any changes to the standards.

“They were not designed to single out women or men,” Guerin said. “It has to do with the way we present ourselves and that represents the company and represents the brand.”

Tamara Rodriguez Trevino, of Dallas, Texas, is an elementary school teacher and wearer of LuLaRoe leggings. The airlines, she said, should be left to their policies for friends and family free travel.

“After reading a few articles and comments about the situation, I feel that, although it may be discriminatory toward women and girls, the airlines have guidelines that have been in place for many years,” she said. “Because they foot the bill for the travel, I feel that they can enforce their policies when applicable. Now removing those said friends of family from the plane seemed excessive to me. Verbal warning should have been given maybe?”

Kim Bongiorno, in central New Jersey, has a 9-year-old daughter who is a leggings enthusiast and caught wind of the controversy on television news. The family travels on United often on frequent-flyer points.

“Ever have to deal with the folds and bunches of jeans on a 5-hour flight, losing circulation and feeling the pinch in your waist when you become bloated?” she asked. “How about people with bad circulation who need to wear compression socks and legging-style pants or sweatpants? Should those who need them for health and comfort reasons be denied a seat on United? Only healthy, very slim, short people who wear jeans/trousers comfortably in cramped spaces are welcome?”

Bongiorno has more questions: What of the decorum of men in clingy trousers that can be revealing? How about men in tight shirts? Men in shirts with sexual sayings or images on them?

Giovanna Bovenzi Cruz, a secretary and consumer services representative from Vineland, New Jersey, wears leggings.

“I feel like the dress code is a little outdated,” she said. “I don’t know any woman or young girl that doesn’t wear leggings.”

Associated Press writers Tamara Lush in St. Petersburg, Florida, and David Koenig and Paul Harloff in New York contributed to this report.