Just closing the loop in case anyone searches for this subject...
Flew US Airways Airbus from LHR to PHL... Used the Britax Eclipse. It DIDN'T have a sticker on it, but I did print out the certificate from their website. Never questioned before or during flight.
Installing the seat was a breeze, but it was very close to the seat in front. Luckily, we were able to move to a row that didn't have anyone in front of us, so that our 21 month old could kick. (tried and failed 50+ times to get him to stop).
He slept 2 hours (nap) going... Coming home was a bit tricker, as they don't turn the lights off for nearly 3 hours (of a 6 hr night flight...), so he only slept 2 hours or so... but he slept.
