Sari Koshetz, a TSA representative, told local TV station WSB-TV the TSA was not in the wrong for letting the child through security, as minors are not required to show identification.
However, she had no comment about the non-existent boarding pass.
"That sounds like we still have a lot of problems, if a child can get through security and get to a plane, and board a plane… you have to ask yourself, where's the ticket? Where's the parent? This is a horrendous breach of security, no doubt about it," security expert Brent C. Brown told CBS46.
Atlanta's Hartsfield-Jackson International Airport has been the world's busiest airport by passenger traffic since 1998, with 104 million passengers passing through in 2017.
When confronted at home, the child's mother was unable to explain how the boy had managed to sneak out and get so close to boarding a flight – telling a WSB-TV reporter, "OK, well you should be at the airport asking them how that happened."
The 11-year-old was returned home to his mother and child protective services had been notified, according to the TV station.