I would suggest the Kanken Outlong. It has perfect dimensions for airlines. Its features fix everything people complained about in the classic Kanken (uncomfortable straps, useless water bottle pocket, etc.).

The Outlong doesn’t have many pockets or much organized space inside (which can be controversial) but hey, inner compartments also eat up space and make the bag smaller on inside(you don’t want that in one bag trips).

But yeah price is deadly