Originally posted by NotUrsula
By all means do ask the airline, but be careful just *how* you ask. Be sure that you not answer the question for them.
If you call up or send an email and say, "I have a high-back booster seat, can my 22 lb. child use it onboard the aircraft?" the airline will just parrot back that notice from the website that Gail just cited. Trust me, they won't look up the real regulation.
However, if you phrase the question as: "I would like to have my 22 lb. child use a carseat on board the aircraft. How do I determine if my seat is approved for use on a plane?" you will force them to tell you what their definition of an approved seat is.
FYI: The real regulation (for US-based carriers only) is 14CFR135.128. You can look up the most current revision for yourself, and print your own copy if you like, by going to http://www.gpoaccess.gov/cfr/retrieve.html and typing in the citation in the search windows. (Once you pull up the regulation, you'll note that for the definition of a booster seat, they refer to 49CFR571.213. You'll want to look at that one, too.)
According to the 14CFR135.128, no US carrier can forbid the use of an FAA-approved CRS for a child who meets the weight recommendation, so long as that child is a fare-paid passenger, and so long as the seat can be properly secured.
It has been my experience that most airline ground personnel and reservations agents have never laid eyes on 14CFR135.128; only flight attendants will know the details without looking it up, and they have been known to get it wrong sometimes, too, if they don't normally work a lot of flights with children on board. If you ask as an open-ended question, the customer-service rep will have to look it up to give you an answer. Don't settle for being told what sort of seat cannot be used, keep at them until they tell you the requirements for a seat that CAN be used.
And yes, PITA that I am, I carried a current copy of 14CFR135.128 with me whenever we flew w/ a carseat. I kept it in a plastic envelope taped to the back of the carseat. Somehow y'all just knew that, didn't you?
I can be a PITA too,
From your link for 14CFR135.128
[Code of Federal Regulations]
[Title 14, Volume 2]
[Revised as of January 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 14CFR135.128]
(D) Notwithstanding any other provision of this section, booster-
type child restraint systems (as defined in Federal Motor Vehicle
Standard No. 213 (49 CFR 571.213)), vest- and harness-type child
restraint systems, and lap held child restraints are not approved for
use in aircraft
NotUrsula,
SWA is not allowing them, neither is Delta and they refer right back to the TSA and their recent (how recent, I don't know) .
Things change, as we all know. I believe this is very recent as this question has been asked a number of times in the past and I have never seen them banned until the other day.
I have enjoyed this banter and I do thank you for being nice, it is appreciated.

I also have a wicked headache from reading those regulations LOL, BUT, the TSA has the final word on it and according to their site, they have banned them from take off and landing and the airlines I quoted have taken it a step further.
Even United has this to say: The following child restraint devices may not be used on board the aircraft: booster seats, belly belts which attach to adult seat belts only, and vests or harnesses which hold the infant to the chest of the adult.
I would be interested to read anything else you may find on the topic.