A number of officials at Manchester airport have been suspended after an 11-year-old boy was allowed to take a flight to Rome without showing a passport or boarding pass.
Liam Corcoran had run away from his mother during a shopping trip in the city and made his way to the airport, reports said.
He followed a family of holidaymakers into an airport terminal and was allowed to pass through five security checks before making his way to the plane.
Security staff did not check whether he was unaccompanied or had a boarding card.
He was allowed to board the flight to Rome without being asked to show either a passport or a boarding card.
Liam was then missed by the flight crew on board who failed to carry out an accurate passenger head-count.
The mistake was only revealed after passengers alerted cabin crew members and the captain radioed back to Manchester.
Police in Manchester called Liam's mother to tell her her son was safe but on a plane to Italy.
When the aircraft landed at Fiumicino airport in Rome, Liam stayed on board for the return flight to Manchester, where he was met by his mother.
British Transport Secretary Justine Greening said it was "an unusual and serious breach".