DALLAS, US - Children flying alone to camp this summer will cost their parents more as US airlines boost fees to help cover rising fuel costs.

Frontier Airlines Holdings Inc, the regional carrier that sought bankruptcy protection last month, last Friday joined AMR Corp's American Airlines and Delta Air Lines Inc in increasing charges for youngsters flying without an adult. The fees are added to the fares for unaccompanied children from ages five to 14.

The charges expand on airlines' efforts to find more revenue from sources other than ticket prices as an 86 per cent increase in jet fuel over the past year widens industry losses.

Carriers are tacking on higher charges for baggage, pets and booking a reservation by phone.

'New and increased fees announced this month will generate several hundred million dollars in incremental annual revenue,' American, the world's largest airline, said last week in announcing bag-check and other charges.

Hundreds of thousands of children fly solo each year on US airlines. Fort Worth, Texas-based American carried about 200,000 unaccompanied minors in 2007 among its 98 million passengers, said spokesman Tim Smith.

American is raising its one-way charge for unaccompanied minors to US$100 from US$75. Delta increased its fee to US$100 each way for all trips; it previously charged US$50 for non-stop service and US$100 on connecting flights. Denver-based Frontier bumped its fee to US$50 each way from US$40.