Children traveling alone on international flights face even closer scrutiny, in part because of the fear of child abductions. In fact, children traveling with only one parent are subject to strict regulations to ensure that a parent is not kidnapping the child from a custodial parent. Any child under the age of 18 who is traveling with one parent to Mexico must show notarized consent from the other parent or a sole custody decree from the accompanying parent. If the other parent is dead, the airline requires the travelers to show a death certificate.
Children need the same documentation, whether passports, visas, or other official paperwork, as adults. It is a good idea to contact the consulate of the country being visited to determine whether there are any special requirements for children traveling alone.