United Airlines is piloting the use of non-binary gender descriptors for customers flying with the company.
The airline company made the announcement on Twitter Friday morning, making it the first U.S. airline to offer non-binary gender options.
Customers will be able to choose the prefix "Mx." during bookings, and they'll have the option of identifying as male, female, undisclosed or unspecified.
"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," United's Chief Customer Officer Toby Enqvist said in a press release.
The airline has been working with the Human Rights Campaign and The Trevor Project in training employees on the new changes, per the release.
Two trade groups approved a new best-practices standard last month that suggested allowing airplane passengers to use non-binary identifiers, reports USA Today. The standard is not a mandate and allows individual airlines to decide whether to implement the option, but most large U.S. airlines have told USA Today they plan to adopt the changes in the future. Marianne Dodson