Trying not to split the family up...car seats in business class are out, economy is terrible, so that leaves premium economy as the hopeful choice.
Age ~15 months.
I'm working to find the rules and whether seats will fit for (front facing) car seats in premium economy. Trip is US > EUR, and if specific airline matters, probably British Airways or Austrian or American.
BA says appropriate seats are fine, but not whether it'll fit. According to their rules, it seems a seat would even go into business, is that correct? Will a seat fit in premium economy (or business)?

Anyone have any knowledge or recommendations, especially if you've done a carseat in premium economy?

Thanks!