Each year, parents fork over hundreds of dollars to airlines’ unaccompanied minors programs to ensure their children traveling alone by plane make it to their destination safely. While most of these trips go swimmingly, a few don’t. Case in point: an Iowa couple says their 12-year-old daughter was left alone at a Houston airport despite paying extra to ensure she was accompanied at all times.

KPRC in Houston reports that the Des Moines couple paid United’s $300 unaccompanied minor fee for their daughter’s recent trip to visit her grandparents in Texas, only to find out on Monday that she was sitting alone at George Bush Intercontinental Airport.

The $300 fee was supposed to ensure that their daughter was escorted by a United Airlines employee at all times. Instead, the parents claim, the girl arrived in Houston where a flight attendant who was supposed to escort the girl left.

After about 15 minutes, the girl’s grandmother found her sitting alone in a hallway.

The girl’s mother then called United upset about the issue.

“I sat on hold with them for 30 minutes and they said, ‘We’re calling customer service to see if we can find her’ and I said ‘I know where she is, but you guys don’t and that’s a problem,’” the mother tells KPRC.

She also posted about the incident on Facebook, noting that “United failed my family. Thankfully my child is safe, but sadly it could have gone SO many other ways.”

United said in a statement that it is “evaluating the circumstances surrounding the matter” and will be following up with the family.

“We are committed to providing exceptional service to each of our customers,” the airline said.

Monday’s incident is just the latest when it comes to airlines misplacing or not holding up their end of the unaccompanied minor program.

In September, JetBlue apparently confused two five-year-old boys flying unaccompanied, putting the boy who was supposed to go New York City on a flight to Boston, and a boy meant for Boston on a plane to New York City.

The following month, the mother of one of the boys sued the airline, which is trying to get the case dropped.

In February, the mother of an 11-year-old girl traveling from New York to North Carolina said the airline failed to notify her that the girl’s flight was diverted to South Carolina.

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