I know this is a very old thread, but I had a question very much related to the topic so it seemed better to post here that create a new one.
I fly Europe to US a lot, so I am used to getting the questions and the stickers when I check in. However, my next flight I am not taking a direct route, rather than flying MAN-EWR I am flying MAN-FRA-IAH. I am also not checking any bags. Thus, my question is, where do I get my sticker? Can I just show up at boarding in FRA without a sticker and tell them I came in on a connecting flight?