Hat-trick chasing Ferrari made a strong start to the French Grand Prix weekend on Friday, with penalty-hit Carlos Sainz leading Charles Leclerc in practice on a hot day at Le Castellet.
The Italian Formula One team are chasing a third win in a row and were fastest in both sessions, Leclerc in the first before Sainz set the pace in the second.
The Spaniard will have at least a 10-place grid drop for Sunday's race due to exceeding his allocation of power unit components.
Leclerc lapped with a best time of 1:33.930 seconds on the soft tyres while Sainz managed a 1:32.527 in the second stint.
Red Bull's championship leader Max Verstappen was second, 0.091 slower, in session one when his car's floor was patched up with tape in a makeshift repair, but more than half a second off Sainz's later pace.
“They've had a quick car all year and we can see they are competitive again this weekend,” said Red Bull boss Christian Horner of Ferrari's pace.
“I think we're competitive in sector one, very competitive in sector two, sector three is probably the bit we've got to tidy up a bit overnight. Lots to look at.”
Verstappen said the team were trying a few things with the car and had not yet got the balance right.
“We'll have a look at it all for tomorrow and of course try be closer than we were today,” said the Dutch driver.
“The long run is a bit better but the tyres are running really hot and it's very difficult to judge really where you are.”
Ferrari won the previous race in Austria with Leclerc after Sainz, who suffered a fiery engine failure in Spielberg, triumphed in Britain.
Verstappen is 38 points clear of Leclerc after 11 of 22 races.
George Russell was fourth in both sessions for Mercedes, who were hoping to be closer to Ferrari and Red Bull this weekend but clearly still have work to do.
Seven-time world champion Lewis Hamilton was fifth after sitting out the first session, with Formula E champion Nyck de Vries taking his place under new rules that oblige teams to run drivers with limited F1 experience in two Friday first free practices.
De Vries was ninth fastest with Hamilton — preparing for his 300th race — watching from the pitwall and offering assistance.
Team boss Toto Wolff said the car's performance, despite fresh updates, was generally “a bit underwhelming”.
“We are still not getting the tyres in an optimum grip window,” the Austrian told Sky Sports television. “It’s a matter of downforce and we’re losing in all corners against Ferrari, on the straights also against Red Bull ...”
Hamilton said it had been an average afternoon but hoped for “a bit of a step” overnight.
Frenchman Pierre Gasly was fifth and seventh, with McLaren's Lando Norris seventh and sixth.
Red Bull's Mexican Sergio Perez, who spun at turn three in the first session but managed to keep his car out of the barriers, was only 10th in practice two.
Polish reserve Robert Kubica replaced Valtteri Bottas at Alfa Romeo for the opening session and was 19th of 20.