The airlines and TSA require adult passengers 18 and over to show valid identification for domestic travel within the United States, such as a driver’s license, passport or one of these. (Note: new Real ID requirements effective May 23, 2023). While the TSA does not require ID for children under 18, some airlines have requirements for domestic travel by minors. Contact the airline for questions regarding specific ID requirements for travelers under 18. Adults and children must have a passport when flying internationally.