NEW YORK >> Should you let your child fly alone?

Parents may wonder after a couple alleged this week that their 10-year-old daughter flying to summer camp was stranded at one of the world’s busiest airports after United Airlines failed to keep track of her.

The girl ultimately made it to camp safely. But the incident highlights some of the risks of children flying alone, including the a little-known industry practice of hiring outside companies to escort kids from gate to gate.

Phoebe Klebahn was flying as an "unaccompanied minor" from San Francisco to Traverse City, Mich., with a connection in Chicago’s O’Hare International Airport. The girl’s parents, Annie and Perry Klebahn, had paid United an extra $99 to assist her during the June 30 trip.

When the first flight landed in Chicago, the company United hired apparently failed to show up.

The parents claim in a letter sent to the airline that their daughter asked for help, including the use of a cellphone, but was repeatedly told to wait by flight attendants. And it appears no one from the airline called the camp after the girl missed her connecting flight.

"She was sad and scared and no one helped," the parents wrote. They shared the letter with media though a family friend who is a business management professor.

The parents did not respond to calls seeking an interview.

The Klebahns wrote that it took them nearly an hour of frantic phone calls to get an answer from United once the camp informed them their daughter hadn’t arrived at the Traverse City airport.

United, part of United Continental Holdings Inc., refused to identify the company that was supposed to look after the girl. It also declined to say if she was ever unsupervised or explain why it took so long to tell the parents where she was.

Flight attendants typically wait with children until the contractor arrives.

In a statement, the airline said it reached out to the Klebahns to apologize and is reviewing the situation. United has refunded the $99 fee and returned the frequent flier miles the family used for the flight.

Parents who need to send their kids traveling alone shouldn’t fret. Hundreds of thousands of kids fly on their own each year — about 160,000 on Delta alone — although the government doesn’t keep detailed data. And while there are occasional mishaps — which would petrify any parent — experts say they represent a small minority of overall trips.