Each airline has their own policy regarding unaccompanied minors. To help with your planning there are a few general policies held by nearly all airlines.
1. Plan on arriving at the airport at least 30 minutes to an hour earlier than you normally would, as you will have to fill out an "Unaccompanied Minor" form at the airline counter. You will also be asked to provide the name of the adult who will be meeting your child at the destination and that individual will have to provide identification before they can take your child.
2. Be prepared to pay a fee for the Unaccompanied Minor service, which can range from $25 to $100, per direction. These fees are not part of the ticket price and must be paid at the counter before they will issue a boarding pass.
3. Restrictions. Unaccompanied minors are prohibited from flying on the last non-stop or connecting flight of the day. This is another reason we recommend you speak to a Travel Specialist as it is not always obvious if a flight is the final one. Many time customers report that a child was booked online to fly on the 5:30pm flight only to be turned away at the counter because the customer was not aware it was the last flight. Some airlines have rules stating that minors can only fly unaccompanied on "non-stop" flights and they can and will deny boarding on a connection flight.
4. Children traveling Internationally must carry a valid passport and have notarized permission in writing from both parents stating that they are permmitted to travel alone. This also applies for children flying with one parent. In that case the parent not traveling must provide a notarized letter stating they grant permission for the child to fly. State the specific date of travel and the child's full name as it appears on thier passport.
Most airlines allow children 15 and over to fly without a guardian or adult without being considered an unaccompanied minor but this is also something you will want to confirm before booking travel. Always consult with the airline prior to departure day. We strongly recommend you call the airline directly to find out what their pollicies are for unaccompanied minors flying alone.