Some airlines might offer special discounts when you book a flight ticket for a child (2 -11 years). The child should be 11 years old or younger at the time of flying. Whether a child discount is applied, depends on the conditions of airline the ticket is sold by.
Exception: In most cases, if the child is 11 years old on the outbound journey and 12 years on the inbound journey, the adult rate will apply. However, this still depends on the conditions of airline.
If you want to book a flight ticket for a minor child (5-16 years) travelling alone, some airlines offer a so-called unaccompanied minor service. Special assistance is then requested from the airline for a fee.
If you would like to add this unaccompanied minor service and you haven’t purchased special services, you will have to pay 39,90€ (or the equivalent in your local currency) administration fee per person. The administration fee is always in addition to the costs charged by the airline for this service.