the Yas Marina Circuit following the 2017 Abu Dhabi Grand Prix, completing 100 laps in his first test with the team's 2017 FW40. He completed an additional 28 laps the next day and finished seventh fastest, with Williams technical chief Paddy Lowe reporting that "there are no issues around" his injuries, though doubts soon emerged about whether certain factors had made the times look better. Williams 2018 season: reserve driver for Williams On 16 January 2018, it was announced that Kubica would become the reserve driver of Williams for the 2018 season. He took part in his first Grand Prix weekend since the final round of the 2010 campaign, in Friday's first practice session at the 2018 Spanish Grand Prix, outperforming teammate Lance Stroll. 2019 season: full-time racing seat Before the final round of the 2018 season, Williams announced that Kubica would race full-time for the team in 2019, partnering 2018 Formula 2 champion George Russell. Kubica chose 88 as his driver number, previously used by Rio Haryanto in 2016. The team struggled during the season, with the FW42 being the slowest car of the field. Kubica finished in 12th place at the German Grand Prix, however was promoted to 10th following penalties for Kimi Räikkönen and Antonio Giovinazzi, scoring his first point since his return to F1 and breaking the record of the longest time between successive points finishes. On 19 September 2019, before the Singapore Grand Prix, Kubica announced his decision to end his stint at Williams after the end of the season. Williams released a statement shortly after, stating that Kubica would see out the remainder of the season but would vacate his driver position for the 2020 season. Kubica's first retirement since his return to the sport came in Russia, when Williams decided to retire his car to conserve parts after teammate Russell's race ended due to a wheel nut issue. Williams were criticised for the decision, particularly by Kubica's personal sponsors PKN Orlen. At the following race in Japan, Kubica criticised the team's decision to remove an upgraded front wing from his car for the race, after he had trialled it during practice sessions. At the 2019 Brazilian Grand Prix, Kubica's Williams mechanics released him from his pit box too early, narrowly avoiding hitting Max Verstappen and holding him up in the pit lane. Kubica ended a difficult season in 19th place in the championship