Yes, you can put your carry-on under your seat, but only if it meets the "Personal Item" dimensions rather than the larger "Standard Carry-on" size. In 2026, airlines have become much stricter with enforcement to maximize overhead bin space. A standard personal item must typically be no larger than 18 x 14 x 8 inches (45 x 35 x 20 cm) to fit safely under the seat in front of you. If you have a larger rolling suitcase (standard 22-inch carry-on), it must go in the overhead bin. FAA and international safety regulations require that the area under the seat be clear of any items that could block an evacuation path or "creep" into the legroom of the passenger behind you. If your bag is even slightly too large to be fully tucked away, the flight attendant will require you to move it to an overhead bin or gate-check it. For those flying "Basic Economy," the under-seat bag is often the only free luggage allowed.