Originally Posted by
Patty2
However, the BA website says the carseat has to fit the dimentions of 17x17" and the Britax Roundabout is 17.7x22" and the carseat has to be CAA approved

The main difference I can find between the FAA & CAA is that they disagree on rearward facing carseats, but that isn't really an issue for us as my son is forward facing.
I've just called BA again to try to find out exactly what carseats they allow, but they could only tell me it has to be able to fasten with a lap belt, be CAA approved and it must fit on the seat.
I would go with the dimensions they state to be sure that your car seat does actually fit and can be secured with just a lap belt plus it will need to be CAA approved with a sticker on the seat indicating this. FAA approvals are completely irrelevent on BA and seats that do not have the required CAA approvals, even if they do have other countries Aviation Authorities approvals, are likely to be refused for use on board. I wouldn't take the risk of not being able to use it as a reult of not following the stated requirements by the airline and CAA. There are a lot of car seats on the market so I wouldn't expect an airline to know all that fit particularly when there are clear guidelines available.