Nico Rosberg wrote himself into the history books on Friday as the first Formula One driver to set a timed lap at the inaugural Russian Grand Prix and first to top the practice timesheets.
The Mercedes driver lapped the Sochi circuit, which snakes past some of the landmark venues used at this year's Winter Olympics, in a best time of one minute 42.311 seconds on a bright morning in the Black Sea resort.
The German's championship leading team mate Lewis Hamilton, who has built up a 10 point advantage after winning the last three races, was second fastest in 1:42.376 as Mercedes continued to dominate.
The team are expected to wrap up the constructors' championship with three races to spare on Sunday, having won 12 of the 15 so far with eight one-two finishes.
Ferrari's Fernando Alonso was the first driver out of the pit lane when the green light came on, leading Force India's Nico Hulkenberg.
McLaren's Jenson Button was the early pacesetter as drivers got to grips with a layout compared to the former Valencia street circuit and Singapore, with the 2009 champion ending the morning as the third fastest.
Alonso was fourth and Danish rookie Kevin Magnussen, Button's team mate, was fifth.
The only Russian regular, Toro Rosso's 20-year-old rookie Daniil Kvyat, was a respectable seventh.
He was joined for the first session by 19-year-old compatriot Sergey Sirotkin, making his debut at a race weekend in the Sauber usually driven by Mexican Esteban Gutierrez.
Williams had a disrupted session when a problem with a tyre blanket damaged a set of Valtteri Bottas's tyres, limiting his running.
All drivers took to the track with stickers of support for Jules Bianchi, Marussia's French driver who was severely injured in a crash in Japan last Sunday and remains in critical condition.
Marussia announced before the session that they would have only one car running this weekend, with Bianchi's assembled and left in the garage as a mark of respect.
Chilton ended the session with the slowest time.
"I don't know how to put into words how truly devastated I am by what has happened to Jules," he had said before the session started.
"It is going to be a very emotional weekend for the whole team, but we will try to get through it and keep praying for Jules."
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