PHOENIX -- Three recent, highly publicized instances in which children traveling alone were put on the wrong connecting flights have compelled America West Airlines to change its policies and brought an industrywide concern about kids flying alone into the spotlight.

The number of children flying on commercial airlines by themselves is on the upswing -- especially in a peak travel period like summer -- and some airline experts worry the potential for mishaps at any airline is too high.

 "As we live in a society where families are divided, there's a lot of flying," said David Stempler, president of the Air Travelers Association, a passenger advocacy group. "But boy, oh boy, it makes me nervous."

 Tempe-based America West's streak began July 14, when an 11-year-old girl flying by herself from Los Angeles to Detroit ended up crisscrossing the country for 18 hours. She was supposed to transfer to the Detroit flight at America West's hub in Phoenix, but was put on a flight to Orlando, Fla., instead.

 A week later, the flight of a 10-year-old San Diego boy going home from Columbus, Ohio, was canceled and the airline failed to tell his father he would arrive more than five hours late.

 On Saturday, two girls returning to San Diego from Texas were sent to the Ontario, Calif., International Airport, about 100 miles north.

 "While our record of transporting these young children has been outstanding, the events of the past few weeks have been both embarrassing and disappointing," America West said in a statement.

 Communication breakdowns caused the mistakes, which are still small compared to the 25,000 unaccompanied children between the ages of 5 and 11 the airline flies each year, America West spokeswoman Patty Nowack said Monday.

 Stempler believes unaccompanied children and connecting flights don't mesh. "This system is a set up for failure," he said. "It scares me to death."

 After the incident with the San Diego boy, America West announced that beginning Sept. 10, unaccompanied children will only be allowed on nonstop flights.

 Starting this weekend, children will have to wear a tag around their neck with their destination code and identifying them as unaccompanied minors, Nowack said.

 Southwest Airlines already allows minors ages 5 to 11 only on nonstop and direct flights and requires a parent to stay at the gate until departure, spokeswoman Kristin Nelson said.

 Southwest and other major airlines give children a button or sticker, fearing a highly visible tag might make the youths targets for criminals. Except for Southwest, airlines charge a fee, usually $30, for children traveling alone, which mostly covers the expense of having them escorted by airline personnel.

 Delta, American and Northwest Airlines don't allow children to be booked on the last connecting flights out of a hub.

 Northwest flew 160,000 unaccompanied children ages 5 to 14 last year and expects a 10 percent increase in 2001. The airline requires every employee who takes care of children to sign off on the child's ticket jacket, spokeswoman Kathy Peach said.

 "It requires a lot of training," Peach said. "There can be no margin of error."

 While no federal agency tracks how many children traveling alone are misplaced, the numbers are likely to increase as families become more mobile.

 Tags and other precautions won't prevent children from ending up thousands of miles from their destination, said Dean Headley, a Wichita State University marketing professor who co-authors an annual review of airline quality.

 "Parents need to take a much more active role," he said. "Not basically let them off the car at the curb and take off."

• Northwest's policies: http://www.nwa.com/services/onboard/minor