My wife and I are flying with our baby on WN for the first time in May. She’ll be just over 1 at the time of flights. We do want to carry on the infant car seat so she gets her own seat and will pay for it if we have to. But I suspect the flights won’t be full. If we don’t get her a ticket and plan to fly with her as a lap infant (gate-check the stroller) and it turns out the flights are not full, can we just bring in the car seat and have her take a seat?