United Airlines has become the first US airline to offer non-binary gender options throughout all booking channels.

The move is in addition to providing the option to select the title “Mx.” during booking and in a MileagePlus customer profile.

Customers now have the ability to identify themselves as M(male), F(female), U(undisclosed) or X(unspecified), corresponding with what is indicated on their passports or identification.

“United is determined to lead the industry in LGBT inclusivity, and we are so proud to be the first US airline to offer these inclusive booking options for our customers,” said United chief customer officer, Toby Enqvist.

“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.”

As part of implementing these new changes, United has worked with the Human Rights Campaign and The Trevor Project on employee training initiatives.

These initiatives include teaching employees about preferred pronouns and the persistence of gender norms, LGBT competency in the workplace and other steps to make United an inclusive space for both customers and employees.

The changes to the booking process are now available.