When making a reservation you can select between two reservation types

WEEKLY: If you prefer to secure a vehicle on a weekly basis, then the weekly option is the best solution. With weekly rentals you can rent a vehicle up to 28 days, then the vehicle must be returned. 

CUSTOM: Sometimes you need a car for a very specific amount of time. This option allows you the rent a vehicle for 4 hours or up to 28 days. Vehicles in this fleet start at model year 2021 and newer and are offered at Residence Inn/Marriott DFW Airport in Irving, TX, Fairfield Inn in Plano, TX and Cypress Waters in Irving TX. 

Checking out both options allows you to see more available inventory and increase your chances on finding a car.