Children not traveling with an adult are allowed, but you must check the conditions with your airline.
Your child must be in possession of valid identity documents required in the country of the destination (a passport or photo ID, visa ...).
Fill in all the forms of the airline with contacts before check-in.
Accompany your child at the check-in counter at least 1 hour before the flight departure, and wait untill take-off.
Your child will be accompanied by the staff to the plane, and board in priority.
At the arrival, your child will be picked-up by the person you have designated, who must be present at the arrival time with an identity document.