Airlines provide age limits for children traveling alone, and provide required services for unchaperoned children in certain age brackets. Services, which for some airlines involve getting the child onto and off of the plane and onto any connecting flights, are provided for kids ages five through 17 --- and are required in some cases -- for children ages five to 11 years old; such as the rules followed by United Airlines. If your child is between five and 11 years old, make sure to contact the airline ahead of time to secure this service. If your child is between 12 and 17 years of age -- and you would like them to be assisted on and off of the plane -- you can take advantage of this service as well.
Certain airlines have more specific travel requirements for younger age groups, and place limits on whether or not children of certain ages can fly on connecting flights without a chaperon. For example, on United Airlines, children ages five to seven cannot fly alone, unless it is a non-stop flight. Be sure to contact your airline in advance to make sure you know the rules.
If you are dropping off your child and picking her up -- or are having someone else meet them -- Alaska Airlines requires that either you, or the other person, get an "escort pass" from the airline; so that you can go with your child to the gate for assistance and supervision. To get this pass and to drop off the child, you will need to fill out a form.
In addition to connections and non-stop flight limitations, some airlines also place restrictions on the times of day that unaccompanied minors can travel. For example, Alaska Airlines does not allow children traveling by themselves to fly between 9 p.m. and 5 a.m. Make sure to contact your airline before you book your flight to make sure that the desired flight is not during hours when your child would not be able to fly.