Packing for Frontier Airlines requires strict adherence to their 14 x 18 x 8 inch (35 x 45 x 20 cm) dimension limit, as anything larger results in a heavy gate-check fee. The best strategy is to use a soft-sided, flexible bag or a dedicated "Frontier-sized" backpack that can be compressed into the airport sizer if necessary. To maximize space, use compression packing cubes to condense clothing and roll items tightly instead of folding them. Wear your heaviest items, such as jackets and boots, onto the plane to save bag space. Place essential items like your ID, boarding pass, and electronics in easily accessible outer pockets, but ensure the bag doesn't "bulge" past the 8-inch depth limit. Avoid using small hardshell suitcases as personal items, as their wheels and handles often push them over the allowed dimensions. It is also helpful to leave a small amount of "buffer room" in the bag so it can be squished down to fit under the seat in front of you, which is the physical requirement for all personal items on this budget carrier.