I have travelled along with both of my kids, this summer I brought Immi (5 months) and Noah (4.5 years) to my parents by myself, and I plan to do it again this summer. To be honest, its pretty easy! Its only one day of my life, and it will be over soon enough. Personally, I wouldn't let my little one crawl up the aisle of a plane, they are super filthy, I am not a germophobe at all, but its gross. I used a baby carried in the airport and I put my bags in her pushchair. I have never seen anyone bring a car seat on a plane, but everyone seems to say they do it, so I must just be on flights where no one brings them. When we flew to Florida in february, we had a bulk head seat and they brought us a skycot which we used on the floor as there was no hardware to hang it, BUT I would have rather been in a 4 across where we could have picked the arm rests up and Noah could have laid across, he was so tired on the way home.
Also, don't forget its illegal to use UK car seats in the US. You might not get arrested, but I would be afraid that my insurance wouldn't pay out
if there was god forbid an accident!