Yes, a 16-year-old can travel alone on Aer Lingus and is considered an adult passenger for the purposes of travel. Aer Lingus officially allows children aged 12 and over to travel unaccompanied on their flights. However, for those aged 12 to 15, a specific "Form of Indemnity" must be signed by a parent or guardian at the airport during check-in. Once a passenger reaches the age of 16, they no longer require this form and can check themselves in and board just like any other adult. It is important to note that while the airline considers them an adult, they are still minors in the eyes of many immigration authorities. If a 16-year-old is traveling internationally (especially into Ireland), it is highly advisable for them to carry a letter of consent signed by their parents, along with a copy of the parent's passport and a birth certificate, to satisfy immigration officers who may have concerns about child safeguarding or human trafficking. Aer Lingus does not provide a "meet and greet" or supervised "Unaccompanied Minor" service for any age group, so the teen must be capable of navigating the airport alone.