Am I required to purchase a seat for an infant?

An infant younger than two years old (at the time of departure for each flight during the journey) may travel on an adult's lap with the purchase of an infant ticket. However, if you are planning to use an infant restraint device/car seat, a child's fare ticket will need to be purchased. An infant car seat may be used for children over two years, and it will need to occupy a standard passenger seat.
The infant must be accompanied on all flights in the same cabin by an adult who is 18 years or older.