Car rental companies are obliged to be open at least 8 hours daily here at the airport. Given that each company usually works around the daily flight times, the opening hours remain at their discretion. However, should you wish to pre-book a rental car, the company will inform you of the pick-up and drop-off process, which is available 24/7, upon booking.
You may find more information on our website: https://www.maltairport.com/passenger/getting-here/renting-a-car/