A car seat is not necessary. If the child is below 2 years of age they will give you a lap belt extender to attach to your seatbelt and strap around the child that you have to use during taxi take off and landing. If they don't give you one you should request for one and you may need to provide the childs passport to show that they are under 2. Also please note that if the child has their own seat you will NOT be eligible for a bassinet. This is based on my experience as I have travelled with an infant (under 2 ) on a child fare with their own seat.