AFAIK, (and this was certainly the case with us), if the child is under 2 but you book a seat for them, you have to provide a car seat for them to sit in on the plane (we did this when we went to Mauritius with Holly at 22.5 months). If you didn't book a seat, then they'd have to sit on your lap for the entire flight.
If the child is over 2, and you have booked a seat for them (which I think you don't have a choice at this age), they don't have to have a car seat to sit in as they are old enough to occupy their own seat.
Holly, July04 & Charlotte, December07
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