Not an expert but our 27 month old has been in a Scenera since she was 7 months old on planes and in rental cars at destinations (at home in our car we use Britax convertibles). Upper weight limit on them goes to 40lbs i believe (double check that) so should last a while.

There are slight spec differences in the models - and I believe only the next is at Walmart?

I find them lightweight, fit through TSA screeners WITH a bag around them, and quickly/easily install on aircraft and rental cars. (We've flown with it on 3/4 of the airlines you listed except Alaska).

Also - they have an easily pointed out "FAA APproved" language sticker on them for curious flight attendants/gate agents.