On Southwest Airlines, a personal item must fit under the seat in front of you and have maximum dimensions of 16.25 x 13.5 x 8 inches (41.2×34.3×20.3 cm). This is slightly more generous than some budget carriers, allowing for most standard backpacks, laptop bags, or large purses. It is important to note that if your item exceeds these dimensions, it will be classified as a carry-on bag, which must not exceed 24×16×10 inches. Southwest is unique among major U.S. carriers for its "Bags Fly Free" policy, allowing two checked bags for free, which often reduces the pressure to overstuff your personal item. However, the under-seat space can be restricted by life vest containers or seat supports, so it is best to use a flexible, soft-sided bag that can be squished if necessary. If you are traveling with a pet, the pet carrier is considered your either your personal item or your carry-on bag, and it must also meet the specific under-seat dimensions to ensure a safe and compliant flight for you and your companion.