We used this on two (back to back) long haul flights (28 hours) and our 2 year old was very comfortable. The seat can be widened and the folding seat was a bonus in transporting it between flights (whilst our son was strapped into a Mountain Buggy bagrider).
I think you can get straps to carry like a backpack, but we fitted it into a doona padded travel bag and still had space for nappy supplies and car seat liners.
The narrow size means I can fit in the back seat of a Nissan Juke with both my kids.
It’s heavier than other car seats, but excels otherwise. Best car seat we’ve ever owned.