My mom has offered to take my 3yo son with her to Philadelphia to visit my sister and neices. This involves flying from St. Louis to PHL. Is there any documentation that is needed for her to take him on an out of town flight? Do, I need to give her written permission for this. I have taken him before by myself and nothing was ever asked about his identity. They checked my ID, of course and just "assumed" he was my child and the child whose name was on the ticket. Would this be any different if he was with Grandma with a different last name? Any help would be great. TIA!!!