Robert Kubica is in action for Williams as the two-day tyre test in Abu Dhabi begins as the team make a final check on whether the Pole is physically able to return to F1.
Kubica's outing, his first in the 2017 Williams car, is the headline act of the event although the likes of Lewis Hamilton, Fernando Alonso and Daniel Ricciardo are also making their final on-track appearances of the year.
Kubica has already conducted two tests in Williams' 2014 car as he attempts to make a full-time return to F1 following the extensive arm injuries he suffered in a 2011 rally crash.
It's believed Kubica is poised to partner Lance Stroll in 2018 so long as he is able to cope with the physical demands and rigours of driving the FW40 in this week's outing.
Kubica also drove a 2017 car for Renault in August at the Hungary test, when he completed 142 laps, but was then overlooked in favour of Carlos Sainz.
Sauber, from whom GP2 champion Charles Leclerc is in action, are the only other team yet to confirm their full driver line-up for next season.