Aitken made his Formula One debut as a race driver with Williams at the 2020 Sakhir Grand Prix as a replacement for George Russell, who was promoted to Mercedes following Lewis Hamilton's positive coronavirus test. Aitken stated before the event he had been "ready since Melbourne [March]" for such an opportunity. He chose to race with the car number 89, in reference to a number he previously used in karting. He qualified for the race in 18th place, within a tenth of a second of teammate and regular driver Nicholas Latifi. On lap 61 of 87, 15th-placed Aitken spun at the final corner, colliding with a barrier and breaking off his front wing. He returned to the pits for a replacement and was able to continue the race, eventually finishing 16th. He later remarked that he had mixed feelings about the race, stating "I think we were doing a really good job up until my little incident. I can only apologise to the whole team", but that there were "a lot of positives to take from the weekend".