Make sure to prepare your child for an unaccompanied minor adventure. In addition, it is vital that you notify the airline in advance.
Airlines generally consider children between the ages of 5 and 14 traveling without a parent or guardian to be unaccompanied minors. Rules vary from airline to airline, but here is what to expect:
•Children ages 5-7 can take a direct fight to a single destination, but not connecting flights
•Anyone under the age of 17 who is flying alone on an international flight may need a signed letter of consent from a parent or responsible adult
•Airlines charge anywhere from $50-$150 each way for an unaccompanied minor fee
More details are here.