Airlines have different policies when it comes to handling unaccompanied minors on their planes.

Major U.S. airlines don't let children under 5 years old fly alone, and they require an extra fee for unaccompanied children from 5 to 11 — or 14, depending on the airline.

Airlines reserve the right to demand proof of age, so have the child's birth certificate or passport.

Get to the gate at least 30 to 45 minutes early to fill out forms, and the parent should stay in the gate area until the plane leaves. Adults meeting an unaccompanied minor at the arrival gate must first obtain a pass from a ticketing agent allowing them beyond the security checkpoint.

Airlines will not administer medicine to children, so if your child needs medicine that he can't administer himself, talk to your doctor before booking.

Here are highlights for the largest carriers. See airline Web sites for details.

AMERICAN AIRLINES:

Fee of $75 each way for domestic and international flights. Ages 5 to 14, and parents may opt to pay for those 15 to 17 to travel as unaccompanied minors. Ages 5 to 7 can only take nonstop or direct flights — those not requiring a change of planes. Ages 8 to 14 can't connect from another airline. Flights must be booked through a reservations agent, not the airline's Web site.

CONTINENTAL AIRLINES:

$50 each way for nonstop flights and $95 with a connection within the United States, Canada and Mexico; $70 and $95 for other international trips. Ages 5 to 14, optional for those 15 to 17. Ages 5 to 7 allowed only on nonstop or direct flights. No departures after 9 p.m. except on international, Hawai'i or Alaska flights or trips of two hours or less. Not allowed on last connecting flight of the day to their final destination.

DELTA AIR LINES:

$50 each way for nonstop and direct flights, $100 with connections. Ages 5 to 14, optional for those 15 to 17. Ages 5 to 7 allowed only on nonstop or direct flights. Can't be booked on last connecting flight of the evening.

NORTHWEST AIRLINES:

$50 each way for nonstop flights and $75 with a connection within the United States, Canada, Mexico, Puerto Rico and the Caribbean; $60 and $90 for international trips. Ages 5 to 14, optional for those 15 to 17. Ages 5 to 7 allowed only on nonstop or direct flights. No departures after 9 p.m. except on international, Hawai'i or Alaska flights or those two hours or less. Can't be booked on last connecting flight of the evening.

SOUTHWEST AIRLINES:

No fee. Ages 5 to 11 and only on nonstop or direct flights not requiring a change in aircraft or flight number.

UNITED AIRLINES:

$99 each way. Ages 5 to 11, optional for those 12 to 17. Ages 5 to 7 allowed only on nonstop or direct flights. Can't be booked on last direct or connecting flight of the day except for connecting to and from international flights.

US AIRWAYS:

$50 each way. Ages 5 to 14 allowed only on nonstop flights, optional for those 15 to 17.