Lewis Hamilton and Mercedes teammate Valtteri Bottas posted the top two times during the opening practice for Formula One's French Grand Prix on Friday.
Defending champion Hamilton clocked the best lap time at 0.140 seconds faster than Bottas.
Red Bulls' Daniel Ricciardo had the third best effort, followed by Ferrari pair Kimi Raikkonen and Sebastian Vettel.
Vettel leads Hamilton by one point atop the standings after seven of 21 races.
The session had one red flag near the end when Marcus Ericsson spun out of control and slammed into the barrier on Turn 11. The right rear of his Sauber burst into flame before the Swede got out. Sauber said he was unharmed.
Hamilton also had a scare when forced to swerve off course to avoid ramming a slow-going Stoffel Vandoorne and slalomed around two rows of bollards before returning to the flow. Hamilton said on his team radio the McLaren driver was going "dangerously slow" when he came upon him.
Later, Hamilton complained his Mercedes was having trouble turning. After coming back out, the four-time world champion quickly went to the top of the timesheet.
This was the first chance drivers had to run on the 5.8-kilometer (3.6-mile) Paul Ricard Circuit, as F1 makes its return to France for the first time in a decade.
The track resting in wooded hills just inland from the Cote d'Azur was basked in the Mediterranean sun and subject to moments of gusting winds.
Raikkonen, Brendon Hartley (Toro Rosso), Esteban Ocon (Force India) and Vandoorne all spun their cars onto the blue-striped run-off areas at Turn Six because of a tricky tailwind but managed to stop before hitting the barrier.
Charles Leclerc (Sauber) twice spun to a brief stop, while Max Verstappen drove wide on consecutive corners and had a near-miss with Sergio Perez of Force India.
Vettel took the lead in the standings two weeks ago in Montreal where he won the Canadian GP after starting from pole position. That victory erased a 14-point lead held by Hamilton after he could manage only a fifth-place finish.
There will be two more practices on Friday and on Saturday before qualifying for Sunday's race.
The last time an F1 race was held here at Le Castellet was in 1990 when Alain Prost won for Ferrari.
(With AP Inputs)