A 20-year-old Minnesota man had settled into his transcontinental KLM flight, occasionally entertaining the two unaccompanied children seated beside him, when he was asked to move. The children needed to sit next to a "mother," a flight attendant said.

The man, who was returning from a mission trip in Uganda, was incensed.

KLM did not reply to an e-mail query about the incident.

"Airlines are acting as custodians of unaccompanied minors, and therefore have the ability to move them to a different seat if they believe that is in their best interest. However, DOT has statutes prohibiting airlines from having discriminatory seating policies, including on the basis of gender or age," a U.S. Department of Transportation spokesman told CNN when a similar incident occurred on a Virgin Australia flight last August. Airlines cannot force a man to move his seat, but they can move the unaccompanied minors, according to the DOT.

In 2010, British Airways paid damages to a man who had filed a discrimination suit after he was forced to move his seat in a similar circumstance. BA quickly changed what had been a formal policy.

In the case of the Minnesotan, the man would have swapped seats, but no woman stepped up. The flight attendant moved the children — ironically, next to the man's sister.

This is tricky business for attendants, who safeguard minors even as they tend to all customers in a busy cabin. Airlines often seat solo children near the crew, who keep a watchful eye. This, clearly, is the best practice — one that forces no assumptions about other fliers.

Send your questions or tips to travel editor Kerri Westenberg at travel@startribune.com, and follow her on twitter @kerriwestenberg.