For a better understanding, you can read the airline policy. Following are the points from the airline policy regarding children and infant travel:

You have to buy a separate plane ticket for children or infants above two years of age.
If the child is less than 15 years, then they cannot travel alone and must be accompanied by an adult.
If you want to sit with your family or children, you must contact the airline, and the executive will arrange your seats together.

For children traveling alone, the airline has an "Unaccompanied minor program." By paying $150, children between the ages of 5 to 14 years will get employee escorts and many special amenities... Read More