Welcome aboard, Mx! United Airlines announced Friday that it is now offering new gender options to accommodate non-binary passengers during the booking process. It is the first airline to do so. 

“Fly how you identify,” United tweeted.

Customers can now identify themselves as M (male), F (female), U (undisclosed) or X (unspecified), in addition to having the option to select the gender-neutral title “Mx.” instead of “Mr.,” “Mrs.” or “Ms.” during booking and in their customer profile. United Airlines issued a statement outlining the new choices. It said the option chosen by passengers must correspond with what is marked on their passports or other official form of identification.

“United is determined to lead the industry in LGBT inclusivity, and we are so proud to be the first U.S. airline to offer these inclusive booking options for our customers,” United’s Chief Customer Officer Toby Enqvist said. “United is excited to share with our customers, whether they identify along the binary of male or female or not, that we are taking the steps to exhibit our care for them while also providing additional employee training to make us even more welcoming for all customers and employees.”

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Booking options are not the only changes United is making when it comes to gender inclusivity. It worked with the Human Rights Campaign, one of the largest LGBTQ rights organizations in the U.S., and The Trevor Project, which provides crisis intervention and suicide prevention to the LGBTQ community, to build a new training program. Employees will now learn about preferred pronouns, persistent gender norms, LGBTQ competency in the workplace and building inclusive spaces for both customers and employees. 

“At the Human Rights Campaign, we believe being acknowledged as the gender you identify with is part of treating everyone with dignity and respect,” said Beck Bailey, acting director of the Workplace Equality Program. “By providing non-binary gender selection for ticketing and the gender-inclusive honorific ‘Mx’ in user profiles, United Airlines is taking an important step forward for non-binary inclusion.”

“The Trevor Project is grateful for United Airlines’ support of our life-saving work on behalf of LGBTQ youth,” the group’s CEO and  Executive Director Amit Paley said. “We are thrilled to bring Trevor’s expertise on the mental health of LGBTQ people to United to ensure its employees maintain safe and inclusive spaces for LGBTQ employees and guests.”

The move comes after industry trade groups Airlines for America and the International Air Transport Association recently approved a new international standard for non-binary passengers, effective June 1. However, implementation of the new gender options are up to each individual carrier. Delta, JetBlue, American Airlines and Southwest have all said that they are working on new gender options for the near future.