You don't *need* a child safety seat, but if you do have one that works for the FAA, it can be nice to have it. Keeps the littles in their seats a bit better. Apart from DS's first flight at a year, we used the carseat until DS was a seasoned traveler, and at 3.5 I gate-checked the carseat instead of bringing it on. He did great, so from now on it's just the lapbelt.