I've flown overseas with Philip 5 times already, and they never looked for a sticker. Their rules (and I mean british airways here) were as follows: We could use the carseat on take off and landing only if it is a 5 point harness. ours wasn't (it was a newborn rearfacing car seat) so philip sat buckled in my lap for takeoff and landing, then sat in his carseat (rather than their bassinette) when the seatbelt signs were off and we were flying normally. Also, we used this same UK-purchased rear-facing car seat in the US. As it didn't have a base or anything and was only secured by the seatbelt, it worked in exactly the same way in both countries.