Mercedes' Lewis Hamilton set the pace during the opening practice session for the Italian Grand Prix, amid the threat of rain at a cool and cloudy Monza.
Hamilton trailed Mercedes team-mate Valtteri Bottas after the Soft tyre runs, having locked up and run deep into the Roggia chicane, but moved clear on the Supersofts with a sequence of quick laps.
Hamilton’s best effort, a 1:21.537, left him 0.435s clear of Bottas, who duly completed a comfortable 1-2 for Mercedes.
Ferrari emerged as Mercedes’ primary opponents, albeit with title leader Sebastian Vettel 1.115s behind Hamilton, as Kimi Räikkönen finished 0.037s further back.
As per the typical 2017 running order, Red Bull occupied fifth and sixth, Daniel Ricciardo just 0.007s in front of Max Verstappen, while Force India took seventh and eighth, Sergio Pérez ahead of Esteban Ocon.
McLaren practised its slipstreaming tactics prior to qualifying, as Stoffel Vandoorne finished in ninth position, with the deficit of its Honda power unit more pronounced at Monza.
Felipe Massa rounded out the top 10 for Williams, ahead of Toro Rosso’s Carlos Sainz Jr., who was the only driver to encounter a major drama when he spun through Parabolica.
Haas’ Kevin Magnussen was 12th fastest, in front of Williams’ Lance Stroll, Toro Rosso’s Daniil Kvyat and McLaren’s Fernando Alonso.
Alonso is set to start from the back of the grid after Honda confirmed that new power unit components will lead to a 35-place penalty.
Romain Grosjean was 16th, ahead of Renault pair Nico Hülkenberg and Jolyon Palmer, while Sauber again finished at the rear of the pack, Pascal Wehrlein faster than Marcus Ericsson.
Ferrari reserve driver Antonio Giovinazzi was initially set to drive Magnussen's car, as part of his Friday programme with Haas, but the team opted to give additional time to the Dane, in the event of wet weather affecting the second session.
As a result, Giovinazzi's run, one of seven planned this year, will be rearranged for a later Grand Prix.
