Yes, a 12-year-old can fly alone on United Airlines in 2026, but they are required to use the Unaccompanied Minor (UNMR) service. United mandates this service for all children aged 5 through 14 who are traveling without an adult at least 18 years old. This service includes a dedicated staff member to escort the child through the airport, early boarding, and supervision during any connections (though United generally requires minors to book nonstop flights only). A supportive peer financial note: there is a service fee of approximately $150 each way for up to two children. You must provide the name and contact info of the adult dropping them off and the adult picking them up, both of whom must show government-issued ID at the airport. Once the child turns 15, the service becomes optional, allowing them to travel as a "young adult" without the extra fee or supervision, provided they are comfortable navigating the airport independently.