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If you're 15, the sky's the limit

Three kids wanted to get away, so they bought tickets at the counter and flew to Nashville, Tenn., on Southwest Airlines. Now their parents are wondering how the trip was possible.

"I just wanted to fly and I had the money," said 15-year-old Bridget Brown, who purchased three airline tickets for herself, a 13-year-old friend and her 11-year-old brother, and hopped a Southwest flight from Jacksonville, Fla., to Nashville, Tenn. — all unbeknownst to their parents.

Brown had $700 in baby-sitting money saved up, and bought the tickets at Southwest’s counter at Jacksonville International Airport.

"He said OK and told us how much it would be and then we paid him," she said in an interview aired on NBC's "TODAY Show" on Friday. "Then he put the flight things on our bags and then he said 'you better run because you might miss your flight.' "

Nobody asked questions or asked for identification. Not the taxi driver. Not the ticket counter. Not security officials or flight attendants or other passengers. So when they landed in Nashville with $40 left and their destination, Dollywood, still hundreds of miles away, they finally called home.

Now their parents are wondering how the trip was possible.

The Transportation Security Administration told NBC News that kids under the age of 18 aren’t required to show ID, just a valid boarding pass.

Southwest said it followed protocol. The incident in Jacksonville "didn’t raise a red flag," spokesperson Ashley Dillon told msnbc.com.

"This has been our policy for awhile now, and most other airlines have the same policy about minors, so we don’t plan to change it," Dillon said.

"Although passengers ages 12-17 are not considered 'legal' adults in the U.S., they may book a ticket and travel unaccompanied — without adult supervision — at any time of day," states the young traveler policy on Southwest’s website. Passengers 12 and older are not considered unaccompanied minors.

Kids between the ages of 5 and 11 are considered unaccompanied minors when "traveling without an accompanying passenger age 12 or over," the policy states.

The children called their parents from Nashville and immediately flew home. Southwest refunded the costs of the tickets.

Minors have the ability to purchase airline, bus or train tickets and leave town without the knowledge of their parents or guardians.

A 15-year-old child, for example, can purchase a Greyhound bus ticket and travel without parental consent (except in Illinois, which has stricter rules for minors).

"We have a number of conditions for minors [under 15] riding alone," said Bonnie Bastian, a media relations manager for Greyhound.

Passengers under 8 years old must be accompanied by a traveling partner who is at least 15, she said.

Furthermore, children between the ages of 8 and 14 years old can travel as unaccompanied minors, but they must be on trips without transfers, the journeys can’t be longer than five hours, the trips must take place during daylight hours and the origin and destination must be full-service stops or company-operated facilities, Bastian said.

Greyhound insists the parent, guardian or legal custodian of the minor complete an unaccompanied minor form. "This form specifically names the person authorizing the trip and the person meeting the child at the destination station and the telephone number(s) at which this person may be contacted," the company’s policy states.

The same basic rules apply to the rails.

Children "15 and older, if they have valid ID, can purchase a ticket and travel," said Amtrak spokesperson Vernae Graham. "That’s our policy."

Perhaps, but it’s not common. "Adults typically buy a ticket," she said.

Richard Bloom, an aviation security expert at Embry-Riddle Aeronautical University in Daytona Beach, Fla., said while this incident amounted to a childhood jaunt, it highlights legitimate safety implications.

"The moral of the story is, at least in other parts of the world, young people are engaged in weapons, planting bombs, testing security," he said. "The point is terrorist groups, insurgent groups, other kinds of transnational groups, what have you, they read the papers, they watch TV, they look at security lapses. And they take that information as they develop their own terrorist operations and anti-government operations."

Msnbc.com staff, NBC News and The Associated Press contributed to this report.