Car seats on aeroplanes

[Stevied82]

I'm looking for advice from anyone who has recently travelled from the UK to USA with a two year old. Our LO isn't a great sleeper and I'm wondering whether it's worth the hassle buying a car seat for the plane. I'd appreciate hearing your experience of this, did it help your LO on the plane? Also which car seat did you use?

Used one once
It was a major hassle to lug on and off the plane
A cushion would be a better option imho

Thanks for your response that's what I'd feared.