Infants and toddlers on airplanes are safest in a car seat with a harness, due to the risk of turbulence. A child who rides in a car seat on the ground should ride in the same car seat on a plane. Air turbulence can be dangerous and can appear suddenly without warning.
Not all car seats can fit on standard airplane seats, which are typically about 16 inches wide, but Safe Kids Carroll County and the Federal Aviation Administration strongly recommend using a car seat if it fits. As in cars, babies under two years old are best restrained in a rear-facing car seat, and a forward-facing car seat can protect toddlers up to 40 pounds or more. Make sure your child's car seat is labeled "certified for use in motor vehicles and aircraft."
You need your child's car seat to travel to and from the airport anyway, and car rental companies might not have reliable car seats available. Your kids are better off in their own car seats.
Children who have outgrown car seats should sit directly on the airplane seat and, like all passengers, keep the lap belt buckled across their thighs or hips. Booster seats cannot be used on airplanes, because they require shoulder belts and airplane seats have only lap belts.
The FAA advises travelers with small children to reserve a pair of seats by a window. Car seats are not allowed in aisle seats or exit rows, where they could block emergency escape routes; they must be installed at a window seat. Most airlines offer a significant discount for children under 2.
Adult air travelers should buckle up, too. Children learn safety behavior by watching parents and caregivers. Safe Kids Worldwide released a study in 2010 showing a strong correlation between adult safety habits and the safety behavior of their children.
Children who ride in car seats on the ground appear to be more comfortable and better behaved when using one on a plane.
For more information about child passenger safety on airplanes, visit the "Flying With Children" page at http://www.faa.gov/passengers or visit http://www.usa.safekids.org/skbu.