Actually Lufthansa does not allow American car seats. I live near Frankfurt and fly them all the time and once mine was taken away. I had the purser brought over and everything. It just turns out that the German Flight Attendants don't usually check but it was my luck that we happened to get a fellow Frenchman (working for LH, living near us) checking it.

It was actually quite funny because by the time the purser got there, he couldn't understand us because we had switched to French and he's all "hey, this is a German airline going to America, we don't need another language going on!"

But I still wasn't happy that my seat was taken away...

I try to book U.S. companies whenever possible so that I can take my U.S. seats along. I've had it taken away by several European companies. Ryan Air, a low-cost company out of Ireland bans car seats entirely.

Btw, someone said that car seats have to go by window. Common misconception. It actually can't block another passengers' access to the aisle. So that means, in a bigger aircraft with two aisles, it can go in the middle.

Double seatbelts are banned on U.S., Canadian and German airlines, among others. They're dangerous for the baby. The U.K. doesn't want babies flying through the cabin, so they require them under 6 months.

Bassinets are no replacement for a car seat and having experience with both, a car seat is much more comfortable and convenient, espeically when alone with three children on 11 hour flights like I do...

hth!
http://flyingwithchildren.blogspot.com