Max Verstappen and Red Bull Racing dominated the opening practice session for the Etihad Airways Abu Dhabi Grand Prix as world champion Lewis Hamilton struggled.
Verstappen tok the headlines on Thursday with a vehement response of his behaviour towards Force India driver Esteban Ocon in Brazil two weeks ago, but he did his talking on the track on Friday afternoon.
His lap of 1 minute, 38.491 seconds was the quickest of the 90-minute session, with teammate Daniel Ricciardo second fastest, 0.454 secs adrift of the Dutchman.
Hamilton, who sealed his fifth Formula One drivers' championship in Mexico in October, was fourth quickest, behind Mercedes teammate Valtteri Bottas.
The Briton, a three-time winner at Yas Marina Circuit in the past, was a second off Verstappen's pace and said on the pit radio he was "quite unhappy".
Ocon was a surprise fifth for Force India, ahead of Kevin Magnussen's Haas. Ferrari pair Kimi Raikkonen and Sebastian Vettel were seventh and eighth respectively.
Sauber's Marcus Ericsson, who is leaving F1 to compete in the IndyCar series in the United States next year, had the biggest drama of the session.
The Swede spun on the exit of Turn 1 and hit the barriers, but he kept the engine running and was able to reverse back on the racing line and continue, albeit with a broken front wing and a puncture.
Robert Kubica, whose return to F1 as a full-time driver in 2019 was confirmed by Williams on Thursday, was slowest of the 20 runners.
The Pole, who stepped in for Sergey Sirotkin in the session, warned on Thursday not to expect a rapid pace as he worked on car set-up, and that proved the case as he was 4.5 seconds off Verstappen's fastest time.
The second practice session begins at 5pm and will also last 90 minutes. Qualifying is on at Saturday at 5pm, with the 55-lap race beginning at 5.10pm on Sunday.