An infant is a passenger 7 days to 2 years old. Infants travel together with an adult passenger and do not occupy a seat of their own. They sit with an extention belt on the lap of the adult and pay only 10% of the regular price.
If you travel on an intercontinental flight there is a limited number of cradle to book. They are avaliable for a baby between 1-9 months old and with a weight less than 11kgs.
Read more about traveling with an infant