Prices for children who fly solo vary by line, trip details

Whether to meet visitation requirements in split families, to visit retired grandparents, to attend school or some other reason, you sometimes need to arrange flights for young children to travel solo. All airlines have “unaccompanied minor” provisions included in their contracts of carriage, augmented by various rules.

In general, the procedures for unaccompanied minors are about the same on any airline. Unaccompanied minors require reservations and adult- price tickets. Adults involved must make firm arrangements to get them to their departure airport and ironclad arrangements for some adult to meet their incoming flights, with all the required documentation. Once an airline accepts a child for unaccompanied travel, it usually places all relevant documents — tickets, meeting instructions and cash for incidental expenses — in a pouch that hangs around the child’s neck. Flight attendants are required to provide onboard assistance, and, where connecting flights are allowed, ground attendants escort the child from arrival gate to departure gate. Airlines generally do not accept unaccompanied minors on flights that stand a substantial chance of interruption: They don’t book unaccompanied minors on the last connection of the day; they generally don’t accept kids on itineraries that require a change of airline or airport; and they cancel any departure likely to run into a weather problem. In the event of an unforeseen problem, airline personnel are required to arrange for monitored accommodations, but airlines work hard to minimize the chances of an overnight delay. Here are the general rules covering domestic flights (international travel is more complicated):

The one common rule among all lines is that 5 is the minimum age for any child to fly without an accompanying adult.

Minimum age for a child to travel alone and unsupervised on an adult ticket: 12 years on American, Hawaiian, Southwest and United; 13 years on Alaska and Sun Country; 14 years on JetBlue; and 15 years on Delta, Frontier, Spirit, US Airways and Virgin America.

Minimum age to travel with unaccompanied minor service on nonstop or through (no plane change) flights: Allegiant does not accept unaccompanied minors of any age; 5 years on other lines.

Minimum age to travel as unaccompanied minors on itineraries requiring connections: 5 years on Hawaiian interisland flights; 7 years on United; 8 years on Alaska, American and Delta; Frontier, JetBlue, Southwest, Spirit, Sun Country, US Airways and Virgin America do not accept unaccompanied minors on connecting flights at all.

Fees for unaccompanied minor service are $ 25 on Alaska nonstop ($50 for connections); $50 on Southwest; $75 on Sun Country; $100 on American, Delta, Frontier (reduced or waived for exalted frequent fliers), Hawaiian ($35 on interisland flights), JetBlue and Spirit; $150 United and US Airways; and $75 to $125 (depending on destination) on Virgin America.

American, Delta, Frontier, Hawaiian, and Sun Country specify that two unaccompanied minors traveling together require only one fee; Alaska, JetBlue, Southwest and Spirit say the fee applies to each child.

Even where not required, most airlines provide unaccompanied minor service to children up to age 17, if parents request it. (Some also offer similar service to cognitively impaired adults.)

A traveler recently reported a problem related to fees for unaccompanied minors. Unlike most other lines, Southwest requires that travelers booking unaccompanied minors must pay the fee at the time of booking. Southwest’s information page says that the fee is nonrefundable if “travel does not take place.” This traveler booked two unaccompanied minor tickets, but had to cancel and rebook. Southwest said he had to pay two more unaccompanied minor fees. He said that the travel did “take place” so he shouldn’t have to pay two fees. Southwest finally relented, but only after a hassle.

All this shows that finding the best deal for unaccompanied minors — especially for two minors — involves a lot of trade-offs and complexities. And it also shows a “new rule” for fees: Unless you’re sure they’re refundable, wait as long as the rules allow to pay them.