According to the announcement, the company's customers now have the ability to choose their gender from among three options, corresponding with the information indicated on their official documents.
"United Airlines today announced it has become the first U.S. airline to offer non-binary gender options throughout all booking channels in addition to providing the option to select the title ‘Mx.' during booking and in a MileagePlus customer profile," the release began. "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," the statement on the airline's official website read.
The statement also explains that the airline has worked in collaboration with the Human Rights Campaign and The Trevor Project to develop an initiative by which the company's employees will be trained.
"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 statement said.
A number of countries have some form of third gender or gender x identification on legal forms as well, including Australia, New Zealand, India, Canada, Portugal, some US states and the District of Columbia, the federal district that houses the US capital.