Sebastian Vettel topped the times for Ferrari ahead of champion Lewis Hamilton in his Mercedes in Friday's opening free practice session for this weekend's Abu Dhabi Grand Prix.
The German four-time former champion clocked a best lap in one minute and 39.006 seconds to outpace this year's title-winner by one-tenth of a second on a hot day at the Yas Marina circuit.
Dutchman Max Verstappen was third for Red Bull ahead of Finns Kimi Raikkonen in the second Ferrari and Valtteri Bottas in the second Mercedes.
Mexican Sergio Perez was sixth for Force India ahead of Spaniard Fernando Alonso and his McLaren-Honda team-mate Stoffel Vandoorne.
Retiremount-bound Brazilian Felipe Massa, in his final Grand Prix, was ninth for Williams and Australian Daniel Ricciardo 10th for Red Bull, 1.7 seconds down on his team-mate's pace after struggling with a performance problem.
"He was running a test programme using reduced modes and we were trying to keep the mileage down," said team boss Christian Horner.
Vettel clocked his best lap with 18 minutes of the 90 remaining after Hamilton and Raikkonen had previously been quickest in a largely uneventful session.