Planning your luggage carefully means checking the Southwest Underseat Size requirements before choosing a personal item. A small, lightweight bag can hold your phone, travel documents, headphones, and other important belongings. Suitable options include compact backpacks, purses, and soft-sided totes that fit beneath the seat. Avoid overpacking because extra items may make the bag difficult to store. Measuring your luggage at home can help prevent unexpected problems during boarding. Always consult the airline’s current baggage guidelines to confirm the applicable requirements and prepare for a comfortable travel experience.