You have nothing to worry about. At check in they ask you how many pieces your stroller collapses into and they give you tags for each part. A funny tidbit, my neighbor just flew aa from New York to London, at check in they weighed her stroller and told her as it was to heavy she would have to check it in. She instead took off one of the seats and told them that it's now 2 pieces so they weighed them each separately and gave her 2 tags and sent her on her way. At the gate she asked them if they want her to take it apart as she has 2 tags for it because it was too heavy, and they just rolled their eyes and said leave it.