In the context of air travel, "checking" a car seat can refer to two things: a safety inspection or baggage handling. At the security checkpoint, the TSA will physically check your car seat; they will run it through the X-ray machine or perform a manual "pat-down" and swabbing if it is too large for the belt. Regarding luggage, nearly all airlines in 2026 allow you to check a car seat for free, either at the ticket counter or at the "gate-check" podium. If you are bringing the car seat onto the plane for use during the flight, a flight attendant will check for the FAA-approved sticker (usually in red text) to ensure the seat is certified for use in an aircraft. It is highly recommended to use a padded "Car Seat Travel Bag" if you are checking it into the cargo hold to prevent damage to the buckles and straps. Remember that booster seats are generally not allowed for use during the flight, though they can still be checked into the hold free of charge alongside your standard baggage allowance.