My first thought is a bunch of 12 year old girls that want to see Taylor Swift. They won't have national IDs. On the other hand, how does it work for children

My first thought is a bunch of 12 year old girls that want to see Taylor Swift. They won't have national IDs. On the other hand, how does it work for children's airline tickets? Again, they won't have national IDs, but we know that children fly all the time -- with and without their parents.