An 11-year-old boy flew to Rome from Manchester Airport by himself without a passport or boarding pass.
Liam Corcoran passed through security without being checked, before making his way on to the Jet2.com flight yesterday.
A Manchester Airport spokesman said: "This extremely serious matter is now being urgently investigated by officials from the airport and airline. It is clear that documentation has not been checked correctly at security and the boarding gate."
More top news
Largely dry across the UK through this evening
A former football coach has handed himself into police shortly after telling a newspaper he had sexually abused youth football players.
Cruz said his debut single combined two of his favourite things - singing and Christmas - and all profits will go to charity.