I am travelling with my 4.5 year old (40 inches and 34lbs) and 2.5 year old (28lbs, 34"). We have a Frontier, a Marathon and a Radian in our car. Which 2 should I bring on the plane and why? Both will be FF on the plane. DD2 rear faces in our vehicle.
I plan to use Travelmates to transport them within the airport.
Do you know what car you will be using at your destination? That might influence our recommendation as well. I think the Radian tends to be easier to install forward-facing in most cars. The Marathon is probably the easier seat to install rear-facing.
I would bring the Radian as one of the seats. I loved how it worked as a forward-facing seat on the plane. Even though it is a heavy seat, it's easier to transport through the airport when it is folded up. It gave my child the most leg room on the plane and we were able to use the tray on the plane. If you want your 2.5yo to use it in the car, then you'll need to bring the rear-facing boot with you separately.
I don't know as much about the Frontier as a travel seat. I've flown with a Britax convertible before. I do not like how it works in the forward-facing position on the plane because it sits up so high and there wasn't much leg room especially if the person in front tries to recline the seat. I like how it works better rear-facing on the plane.
Melanie