Yes, children are absolutely allowed to bring a backpack on a plane, provided they have their own purchased seat. For most airlines, a child's backpack counts as either their "personal item" (if it fits under the seat in front of them) or their "carry-on bag" (if it goes in the overhead bin). It is a fantastic way to keep them occupied, as you can pack it with snacks, tablets, coloring books, and a change of clothes. If you are traveling with an infant as a "lap child" (under age 2 without a separate seat), policies vary; many airlines allow one diaper bag per infant in addition to the adult's allowance, but a standard school-sized backpack might be restricted unless it fits within the adult's personal item quota. Always ensure the backpack isn't too heavy for the child to carry through the terminal, though many parents end up "double-bagging" it over their own luggage during long walks.