Ferrari's Kimi Raikkonen set the pace in the first Russian Grand Prix practice on Friday with fellow Finn Valtteri Bottas close behind for Formula One champions Mercedes.
Raikkonen, who has not stood on the podium since last July and has scored half the points taken by team mate and championship leader Sebastian Vettel this season, lapped in one minute 36.074 seconds.
Vettel, chasing his third win in four races for resurgent Ferrari, suffered a spin but was fifth fastest with Red Bull's Max Verstappen fourth on a sunny morning with snowy mountains as a backdrop.
Bottas was a mere 0.045 slower than his compatriot with team mate Lewis Hamilton, Vettel's closest rival, third fastest but 0.607 slower than Raikkonen after going off the track several times.
Sochi's street circuit, winding around the landmark venues of the 2014 Olympic Park, has favoured Mercedes since its debut three years ago with the champions leading every lap of every race there.
Triple champion Hamilton won in 2014 and 2015 with now-retired team mate Nico Rosberg triumphant last year on his way to the title.
Raikkonen and Bottas also have good records in Sochi, however, with the 2007 world champion finishing third last year and the latter taking the first fastest lap of his Formula One career in 2014 when he also came third for Williams.
"As a team I think we've come a long way from the last few years," Raikkonen had told reporters on Thursday. "Yes, there are still things that we have to improve all the time and do better but that's the same with everybody.
"Are we at the same level as them (Mercedes)? I donât know. It's not far off, let's put it that way."
While Finns topped the timesheet, another flying fin briefly halted the session.
Force India's Esteban Ocon brought out the red flags when the engine cover, with its distinctive 'shark fin', flew off the car.
Russian reserve Sergey Sirotkin replaced Germany's Nico Hulkenberg at Renault for the session but the car broke down on track before he could do a timed lap and was pushed off by marshals.