Story highlights The TSA says the boy went through security with all other passengers

A child, apparently without a ticket, boards a flight from Minneapolis to Las Vegas

Mid-flight the Delta crew becomes suspicious of the child's "circumstances"

The 9-year-old is thought to have been at the airport the day before as well

A flight to America's adult playground, Las Vegas, had an unusual passenger last week: a 9-year-old boy traveling on his own, apparently without a ticket.

The boy went through security with all other passengers, the Transportation Security Administration said in a statement, but officials are still trying to figure out how he did it -- and how he then got on the flight.

Patrick Hogan, a spokesman for Minneapolis-St. Paul International Airport, said the crew of Delta Flight 1651 "became suspicious of the child's circumstances" during the flight from Minneapolis to Las Vegas. Crew members got in touch with authorities in Las Vegas and turned the boy over to Child Protective Services, Hogan said in a statement.

"Fortunately, the flight crew took appropriate actions to ensure the child's safety, so the story does have a good ending," he said.

Delta said it takes the incident "very seriously" and is working with authorities.

The airline spells out its policy about children flying solo plainly on its website.

JUST WATCHED 9-year-old sneaks on flight to Vegas Replay More Videos ... MUST WATCH 9-year-old sneaks on flight to Vegas 01:31

JUST WATCHED Is U.S. airport security flawed? Replay More Videos ... MUST WATCH Is U.S. airport security flawed? 03:38

Children between the ages of 5 and 14 may travel alone as part of the unaccompanied minor program. Someone from Delta pays special attention to the children, walks them on board, shows them their seats and even introduces them to the cockpit crew, time permitting, Delta says, adding, "Kids love this part."

Airport officials reviewed security footage and don't think the child had a ticket, CNN affiliate KARE reported.

The boy, a runaway from the Twin Cities, spent a good amount of time at the airport before boarding the plane, KARE said.

He was there the day before, the station reported, citing airport officials. He passed his time by taking luggage from a carousel, bringing it to an airport eatery and then ditching it, asking a server to watch the bag "while he went to the restroom."

The following day the child took the train to the airport, cleared security and made it to Las Vegas nearly without detection.

"Obviously, the fact that the child's actions weren't detected until he was in flight is concerning," Hogan wrote. Still, 33 million people travel through Minneapolis' airport every year, he noted. "I don't know of another instance in my 13 years at the airport in which anything similar has happened," he said.

A flight security expert said it's very concerning that the child made it through several security checks.

"All of this (security) since 9/11 has been to keep us safe. And it has, but still we have gaping holes, and this is a perfect example of it," Terry Trippler of ThePlaneRules.com told KARE.

The incident may be a first for Minneapolis, but over the years other airports have had similar incidents.

In 2007, another 9-year-old managed to fly from Seattle to Phoenix to San Antonio before being found out. He had a boarding pass, though. His mother told CNN her son gave ticketing agents a fake name.