If they are travelling from the US, you need a notarized letter(or letters), from the parents/guardians stating that permission is given for the minor to travel alone. It also must state the name and passport/cedula # of the person meeting them at the airport. When checking in for the flight, the parent with the minor is given a gate pass, and must stay with the minor until they have boarded. On the other end, the person meeting them upon arrival should go to the airline desk, identify themselves, and explain that they are picking up an unaccompanied minor. They will be given a pass as well, and should be allowed to greet the minor before baggage claim. Check with the airline office in the airport of arrival for specific instructions, as they all have differnt meeting spots where the children are turned over to the responsible party.