A mother from Arizona is suing Delta Air Lines because she was unable to purchase a plane ticket for her nonbinary child due to the airline’s lack of gender options during the booking process.

Dawn Henry, 52, said in a Twitter thread Thursday that she was trying to buy a surprise plane ticket for her adult child when she discovered Delta only offers male and female gender options. Henry’s 21-year-old child is nonbinary, which means he or she does not identify as exclusively male or female, and they have a “X” gender marker on their birth certificate and Washington state driver’s license.

This incident occurs three years after Delta and other major US airlines announced that they would update their booking tools to accommodate nonbinary passengers. At least two of the other airlines, American and United, already offer a nonbinary-inclusive drop-down menu during the booking process.

While Henry remains dissatisfied with the situation, she hopes that speaking out will prompt changes throughout the airline industry.

When Henry contacted Delta about the lack of gender options, a Delta supervisor directed her to the company’s policy, which only recognizes male and female genders, according to Henry.

The Transportation Security Administration, an agency within the United States Department of Homeland Security that oversees travel security, advises travelers to “use the same name, gender, and birth date as indicated on your government-issued ID” and states that at the security checkpoint, a TSA officer “will ensure the identification and boarding pass are authentic and match.”

When asked about Delta’s lack of a nonbinary gender option and why one was not added soon after the 2019 announcement, a company spokesperson stated that it is not an easy fix that requires the involvement of multiple departments. The representative did, however, state that the addition would be available later this year.

“Delta Air Lines is a proud, long-time supporter of the LGBTQ+ community, and we understand that being seen and acknowledged is part of having an equitable travel experience,” said a spokesperson. “While we quickly shifted our focus in early 2020 due to COVID to assisting customers in navigating the rapidly changing environment and government regulations, we are back on track to offer a non-binary gender option in our booking systems in 2022.”

Delta’s current policy, according to Josh Block, a senior attorney with the American Civil Liberties Union’s LGBT & HIV Project, is discriminatory, despite the fact that several courts have upheld the rights of the transgender community.

“There’s a major issue with Delta and possibly other airlines not adapting their computer system to the reality that people have official government documents that recognize their nonbinary gender identity,” Block said. “If an airline has a policy that prevents nonbinary people from flying, that would clearly violate that sex prohibition.”

Delta isn’t the only airline that hasn’t added nonbinary gender options since a joint announcement by six major airlines in 2019. Alaska, JetBlue, and Southwest do not offer any options other than male and female.

Following the incident, Henry stated that she will not pursue legal action.

“I am glad they are finally promising to follow through on a commitment they made four years ago,” Henry said, adding that the airline has not responded directly to her. “I will not relent until every U.S. airline that has a discriminatory reservation system makes the long-overdue changes.”

Nonbinary individuals are legally recognized on identification documents in more than a dozen states, including New York, California, New Jersey, and Maine. As more states adopt the gender marker X, Block believes it is critical for businesses to do the same.

“This is not something that any business should just be sitting back and wiping their hands of,” Block said. “Businesses have an obligation to make sure that nonbinary people have equal service, and if that requires investing money to update your computer system, then that’s what a business needs to do.”