American Airlines has confirmed to USA Today that they now allow customers flying on their airline to identify as non-binary designations ‘U’ or ‘X’ when flying.

The report also notes that American “worked with LGBTQ organizations The Human Rights Campaign and The Trevor Project on training employees in conjunction with these updates.” This includes training for employees to being respectful of traveler’s preferred pronouns such as ‘they/them’ and ‘ze/zir’.

Related: Southwest Airlines updates its family boarding policy to be LGBTQ inclusive

This followed a decision by the industry trade association Airlines for America (A4A) in February, paving the way for its members – which includes United, JetBlue, Southwest, and other airlines – to allow people with non-binary designations to travel freely without having to identify as solely male or female. The International Air Transport Association (IATA) made a similar decision as well.

Currently, only some states and territories – including Oregon, California, Minnesota, Colorado, Arkansas, and the District of Columbia – allow non-binary people to have preferred gender designations on their official documents other than ‘M’ or ‘F’, including those used for travelling.

As soon as the A4A’s ruling went into effect in June, United was the first member to implement training for employees and options allowing passengers to travel under designation that most conforms to their identity. They allow for the designation of ‘Mx’ for travelers to choose. That same month, Air Italy followed suit by allowing ‘X’ for its customers in Europe.

The currently acceptable symbols are now ‘M’, ‘F’, ‘U’, and ‘X’. ‘U’ and ‘X’ were implemented with travelers in mind who would rather identify as unspecified or undisclosed than under either male or female. Passengers must carry a passport or other identity document that has a gender marker other than ‘M’ or ‘F’.

“We recently completed a system update to offer non-binary gender selections…taking care of our customers and team members is what we do, and we are glad to be able to better accommodate the gender preferences of our travelers and team members,” company spokesman Ross Feinstein told USA Today. Delta, Alaska Airlines and Southwest now all plan to follow suit, according to the paper.