Yes, a wedding dress counts as one of your allowed carry-on items (either your carry-on bag or your personal item, depending on its size). Most airlines recommend bringing your dress on board rather than checking it to avoid the risk of loss or damage. You should transport it in a high-quality, opaque garment bag. Once on the plane, you can politely ask the flight attendants if there is space in the onboard coat closet; while many crews are happy to help, these closets are not guaranteed and are often reserved for First Class. If the closet is full, you will need to carefully lay the garment bag flat on top of other bags in the overhead bin. To be safe, board early (using priority boarding if possible) to ensure you have enough bin space, and always carry a portable steamer to handle any wrinkles that occur during transit.