I always pack 3 or 4 extra diapers in my carry-on, and if I'm wet before the check point, I'll change my diaper before I go thru... As far as carrying extra diapers, once when I flew, the plane was delayed due to storms, and after 2 hours, they canceled the flight!! However, everyone's check-in luggage was sent on another flight. Then they told us that we could fly out the next day!! So I'm in an airport overnight, all my clothes and diapers were in my checked bags, on another plane. Fortunately, I had two diapers in my carry-on bag, which saved me.