Using a car seat on an airplane

You do not have to use a car seat on an airplane. But you might want to. First, the background information.

The US Federal Aviation Administration, the US National Transportation Safety Board, the American Academy of Pediatrics, and the Australian Civil Aviation Safety Authority all appear to agree on the following basic principles:

All passengers are always safer on an airplane when properly restrained, period. Being properly restrained will make a baby significantly safer on an airplane.
Unrestrained babies in airplanes are subject to more risks than unrestrained adults. It takes less turbulence to fling them around the cabin, and once they have gotten misplaced in the cabin, they cannot find themselves and can get trapped under seats and in small spaces, making them hard to evacuate. (There isn't good data on this because adults are usually belted. However, this article suggests that unrestrained babies are up to 9.6 times as likely to die in an airplane accident than restrained adults.)
A baby in a bassinet is an unrestrained baby.
Restraining babies with an adult seatbelt is simply unacceptable and drastically increases the chance of injuring the baby.
Restraining babies with an addition to an adult seatbelt (an extra loop) keeps them from flying around the cabin, which is good, but significantly increases the chance of other injuries to the baby, which is bad. [The US and Australia differ on whether this tradeoff is acceptable, but agree that it will result in some babies that would have died of head injuries living with abdominal injuries and also some babies that would have had no injuries having abdominal injuries.]
The best possible way to restrain a baby on an airplane is an aviation-approved child restraint (that is, a car seat certified for airplane use). This should be installed according to the manufacturer's label, even if that means facing the rear of the airplane. Aviation-approved child restraints are tested for airplane safety as well as car safety.

The FAA believes that unrestrained babies in airplanes are safer than restrained babies in cars. The NTSB does not. The AAP wavers, but appears to side with the NTSB currently.

Note that the UK CAA does not agree on these points. In particular, although their own test data appears to agree with point 5, they still require the use of loop restraints for babies under 6 months (I think this is scandalous, although admittedly the FAA allowing completely unsecured babies is no better) and their test data does not quite agree with point 6. The CAA believes that the best available way to restrain a baby on an airplane is a forward-facing aviation-approved child restraint, and that rear-facing seats, when secured with an aviation lap belt, do not provide as much protection, and they have crash-test data to support this belief. There is not enough data online for me to compare the tests that lead the UK CAA and the US FAA to different opinions. I tend to believe the FAA; that might be just jingoism, but I think it's partly because the FAA and the NTSB, who don't speak in chorus, have the same belief. Also, because the CAA still requires loop restraints and forbids carseats for babies under 6 months in spite of their own data showing that carseats are better, I don't trust them. I have heard it suggested that the carseat lobby is responsible for the US position, but I doubt that. First, the carseat lobby doesn't appear to be wildly successful in the US (not compared to, say, Sweden, where carseats are mandatory until age 12). Second, the FAA and the NTSB are non-elected regulatory agencies, not invulnerable to lobbying, but nowhere near as susceptible to it as lawmakers. I think it's an honest difference of opinion.

Good and bad points about taking a car seat on board:

Good:

The baby is as safe as possible.
The baby has a familiar environment. Our baby sleeps well in her car seat, and is much easier to contain in it.
You are guaranteed not to have to hold the baby for takeoff, landing, and turbulence, which you will have to do even if using a bassinet otherwise.
You know that you will arrive at the other end with your car seat intact, ready to install in a taxi or rental car, not damaged or lost in the luggage handling process.
You will have a ticket and therefore a luggage allowance for the baby -- one friend of our acquaintance says that on many flights getting the baby a ticket is actually cheaper than paying extra luggage penalties, for the family he travels with.

Bad:

You have to pay for a seat to guarantee you will be able to use the car seat.
You have to lug the car seat around the airport (and not by the straps as that may damage the seat).
Some airlines will actually treat you less well because you have paid for a seat and wish to use a car seat. They may, for instance, refuse to let you have a bassinet if you have paid for a seat.
Some airlines won't let you use an approved seat. US airlines must let you use an approved seat according to its label if you have purchased a ticket, but they don't always know the rules. Australian ones are not required to let you use a car seat, but in our experience usually give in with bad grace if threatened sufficiently.
Rear-facing seats give airplane crew fits. Be prepared to argue persuasively.

These are all common and false reasons to avoid using a car seat:

If the plane crashes, everybody will die anyway. Nope; this article shows significantly higher death rates for unrestrained babies than for restrained adults. The NTSB also cites two crashes, within a few months of each other. In one, an unrestrained baby died while the baby's belted mother was lightly injured. In the other, the mother received similar injuries while her carseat restrained baby was uninjured.
Car seats are meant for cars, they don't really have anything to do with airplanes. Not true for aviation-certified car seats. The FAA works with the NTSB to determine standards and crash-test seats for airplanes, not just for cars.

Here's at least one reasonable argument not to use a car seat:

Airplane crashes are very very rare. You almost certainly do more hazardous things with your baby on a regular basis.
Not all foreign carriers will allow you to use car seats; it may limit your choice of airlines.

Links

The FAA recommending car seats

The AAP recommending car seats

NTSB recommending requiring car seats

CASA recommending car seats

The UK CAA allowing car seats after 6 months

Print these before flying

US carriers: The FAA officially requiring airlines to let you use a car seat, including facing backwards (See page 7).

Australian carriers: CASA official car seat rules

Canadian carriers: TCCAA rules

Information for dealing with the airline

The rules that apply to an aircraft are those of its country of registry; this will normally be the country for the airline that owns the airplane. Note that on a code-share flight, the rules of the carrier operating the flight apply (that is, if you fly a United flight number but a Qantas airplane, it's Australian rules, not US ones, that apply). It does not matter what country you are flying to/from on an international flight, the rules are those of the country of registry.

	Forward-facing carseat	Rear-facing carseat	Loop belt	Unsecured baby in lap	Carseats allowed	Location of carseat
Australia	Permitted 6 months- 4 years as long as seat is used according to manufacturer's instructions; up to the airline to decide whether or not to allow carseats at all.	Permitted from birth as long as seat is used according to manufacturer's instructions; up to the airline to decide whether or not to allow carseats at all.	Permitted 0-24 months	Forbidden	(a) seats complying with Australian design standard AS/NZS 1754 for infant car seats which are secured in the aircraft in a manner consistent with the seats' design criteria. As this standard requires a 3-point attachment, a top tether, in addition to the fastened lap belt, must be fitted. (b) seats accepted by the Federal Aviation Administration of the United States of America as meeting the Technical Standard Order TSO-C100b or seats which have two markings: “This Restraint is Certified for Use in Motor Vehicles and Aircraft” in red lettering and “This seat conforms to all applicable Federal motor vehicle safety standards”; (c) seats approved to Canadian Motor Vehicle Safety Standard (CMVSS) No. 213 entitled “Child Restraint Systems” or CMVSS No. 213.1 entitled “Infant Seating and Restraint Systems”; (d) seats accepted by the Civil Aviation Authority of the United Kingdom for which general guidance can be found in the CAA Official Record Series 4 General Exemption – Child Restraint (Public Transport); (The Type 2040-1 Carechair, manufactured by Aviation Furnishings International Limited has been accepted by the CAA(UK) as a child safety seat specifically designed for aircraft applications) (e) seats meeting European Safety Standard requirements of ECE Regulation 44.	Not blocking any passenger's access to the aisle (in a window seat or the middle seat of the middle section); not in an exit row, the row before, or the row after.
Canada	Permitted when used according to manufacturer's instructions. Up to the airline to decide whether to allow.	Permitted when used according to manufacturer's instructions. Up to the airline to decide whether to allow.	Forbidden	Permitted 0-24 months	(2) The Canada Motor Vehicle Safety Standard (CMVSS) No. 213 of the Motor Vehicle Safety Regulations entitled "Child Restraint Systems",effective May 11, 1984; (3) The Canada Motor Vehicle Safety Standard (CMVSS) No. 213.1 of the Motor Vehicle Safety regulations entitled "Infant Seating and Restraint Systems", effective September 1, 1982; or (4) The Federal Motor Vehicle Safety Standard, (FMVSS) No. 213 (FMVSS 213), entitled " Child Restraint Systems", published by the Government of the United States, and complying as follows: (i) for Standard FMVSS No. 213 effective previous to amendment dated February 26, 1985 and manufactured after January 1, 1981; (However Vest and harness-type child restraints are not acceptable); (ii) for Standard FMVSS No. 213 amended effective February 26, 1985, and manufactured after that date, when approved for use in aircraft and carrying the label, printed in red lettering,"This restraint is certified for use in motor vehicles and aircraft; and (iii) child booster cushions, as authorized in standard FMVSS No. 213, are not permitted for use on aircraft in Canada.	Not in an exit row, not blocking access to an aisle
New Zealand	Probably permitted up to 4 years-- rules do not specify. Airlines are not required to allow carseats.	Permitted up to 4 years. Airlines are not required to allow carseats.	Permitted up to 4 years.	Forbidden	Not specified.	Not specified.
UK	Permitted 6 months to 24 months; up to the airline to decide whether or not to allow	Forbidden	Required 0-6 months; permitted 6-24 months	Forbidden	a) A car-type safety seat (“safety seat”) must have a well-defined shell and, where there is a separate shell and understructure they must be securely attached to each other. b) A safety seat must be of such a design that a child can easily and quickly be secured in or removed from the seat. c) A safety seat must have a single release type harness which at least secures a child's lap, torso and shoulders. d) The single release device for the harness of a safety seat must be of such a design as to prevent unreasonably easy release by the child occupying the safety seat. e) The harness straps of a safety seat must be of a minimum width of 1"/25mm. f) Any lift-type adjusters on the harness straps of a safety seat must be of a type that require a positive angular lift to release.	Not in an exit row, or the row before or after; in a window seat (note that the middle is not OK per regulations). Only one per row unless the children are in the same family.
US	Permitted until child is over 4 years and 40 pounds when meets manufacturers requirements (you may not use a carseat forward-facing if the manufacturer's instructions say it must rearface at your baby's age/weight). Airline must allow if you have purchased a seat.	Permitted when meets manufacturer's requirements. Airline must allow if you have purchased a seat.	Forbidden	Permitted 0-24 months	The CRS should have a solid back and seat The CRS should have internal restraint straps installed to securely hold the child to the CRS The CRS should be labeled stating that it has been approved for aviation use, and The CRS should have instructions on the label which must be followed; (labels for approval from other countries are allowed and therefore may vary)	Not in an exit row or the row before after; not blocking any passenger's access to the aisle (in a window seat or the middle seat of the middle section).

Airline (# of flights)	Hassled about car seat	Seated illegally	Preboarded	Policy link
Southwest (6)	No; very helpful, once actually complimented us on it	No	Yes; jumped to front of line when arrived late.	Southwest policy [Strongly encourages car seat use and explicitly mentions rear-facing. Go Southwest!]
America West (4)	No; one very mild confusion, one positive comment	No	Yes	America West policy [Mentions rear-facing but conflicts with FAA regulation]
United (6)	No	No	Once. Never actually stopped from pre-boarding, although told it was against policy once	United policy [does not mention rear-facing or particularly encourage car seat use]
American Eagle (1)	Mildly	Yes	No	AA policy [Mentions rear-facing; does not particularly encourage car seat use]
Qantas (4) Why we hate Qantas	Massively (4)	Yes (1)	Yes (3)	Qantas policy [Mentions rear-facing; requires pre-approval via special handling to use car seat.]

<>Airlines that do not allow carseats

These are just the ones we happen to have noticed.
Virgin Blue (Australia)
Alitalia (Italy)

Buying tickets for a carseat

Most airlines offer discounted child/infant fares. Usually these are not purchaseable from the airline's website, and other travel websites differ in how well they deal with them. Orbitz is generally the best. Always price a discount adult ticket against the child/infant fare; you may find the adult ticket a better deal and it is perfectly OK to buy an adult ticket for a baby. If you are looking at an infant fare, be sure that it is a fare for an infant in a seat because many times it is the cost for a lap baby. Yes, they charge extra for a baby with no seat -- but you usually get some minimal baggage allowance, if that makes you feel any better. No, it doesn't even guarantee you'll get a bassinet.

What to do about an infant carrier with a separate base

If you are required to use the base to belt the carrier into a car, you will need to take the base. However, many infant carriers can be used without the base. If you have one of those, I recommend bringing just the carrier if you have 2 adults to 1 baby. If there is only 1 adult with the baby, you may find that taking the base allows you to put the baby down while you install the base in the airplane. It's still a nuisance to carry through the airport.