Aitken confirmed his departure from Renault as his test driver role was getting him no closer to potentially finding his way on to the Formula 1 grid with them.
Now Aitken is taking a different path with Williams which will include trackside integration, simulator work and, most importantly, on-track experience in a Friday FP1 session.
Aitken said: “It is a great honour to join ROKiT Williams Racing as their Reserve Driver for the 2020 season.
“Williams is a team with strong heritage, and continued longevity, and I’m looking forward to directly contributing to their development through my simulator and testing work.”
Claire Williams, deputy team principal, added: “It is obvious from what Jack has achieved so far he is a young driver with a great career ahead of him and we believe he has the right credentials to reach the top in the sport.
“Jack has proved his ability in FIA Formula 2 and GP3 and we look forward to seeing what he can achieve as the team’s Official Reserve Driver.”
Aitken now joins former Red Bull junior Dan Ticktum, Israeli driver Roy Nissany and W Series champion Jamie Chadwick in the reserve ranks at Williams.
🗣️ "I'm really looking forward to seeing what I can contribute." pic.twitter.com/6Ca4p0odpo
— ROKiT WILLIAMS RACING (@WilliamsRacing) February 4, 2020