American Airlines is the latest carrier to offer passengers a gender option beyond male or female when booking their ticket. The new choices are U for unspecified or undisclosed and X for those who don’t identify as male or female, the Dallas Morning News reports. “We recently completed system updates in an ongoing effort to offer nonbinary gender selections,” American said in a statement. United Airlines became the first to expand the gender options in the spring, but a number of other major carriers are following suit.