Car seats can be lost or damaged when checked, and children under 40 pounds are safer on a plane when riding in a car seat. A car seat check bag will only prevent some superficial damage, not structural damage, so if you really need to check your car seat it’s best to use a strong cardboard box.
Can you bring a baby car seat on the plane?
You are allowed to bring aboard your own car seat for use by infants as long as it is certified as suitable for air travel. Babies younger than 2 years can be held on the lap of an adult or use car safety seats. Any child aged 11 or less is also permitted to use their own car seat on board of the plane.