Lewis Hamilton finished second with Max Verstappen third for Red Bull – the top three covered by just 0.058s.
In sunny conditions at Imola, the majority of the peloton started very early in the hour-long session, with several drivers taking advantage of first place in a frenzied 15-minute opening.
Ocon set the best initial time at 1m26.246s, but the benchmark was quickly lowered as the riders explored the 3-mile track on hard tires.
Valtteri Bottas’ 1m20.345s lap on the hards was FP1’s first real flying lap, but it was quickly beaten by Alfa Romeo’s Kimi Raikkonen before the Mercedes rider reclaimed first place with a 1m19.312s.
Perez then lowered the benchmark first place to 1m19.205s before Ferrari’s Carlos Sainz Jr beat that with a 1m18.764s on the hard rubber with white walls.
Hamilton used the same tires to briefly claim first place with a 1m18.257s before Sainz improved again as his race continued with two new fastest laps which brought the P1 time to 1m17.682s in 15 minutes – just before Yuki from AlphaTauri. Tsunoda had a brief passage through the gravel of the Tamburello chicane.
After a 10 minute lull in action Pierre Gasly went fastest with a 1m17.470s and after another 10 minutes Bottas again took first place in a 1m17.396s – just before Hamilton cut the grass to the Variant Alta.
Sainz then regained first place with a 1m17.296s, the session then being signaled with the red flag following the clash between Ocon and Perez.
The Red Bull stopped at the exit of the Villeneuve chicane with its left rear tire torn from its rim, the Alpine d’Ocon stopped further down the road with damage to the front right of its car. The stewards summoned the two drivers to explain the incident after FP1.
After just over 10 minutes, the session resumed, with the drivers switching to soft tires to set a series of quick laps at the end of FP1.
Lewis Hamilton, Mercedes W12
Photo by: Mark Sutton / Motorsport Images
Hamilton took first place with a 1m16.892s with just under 10 minutes of the session remaining, before Verstappen’s flying lap on the soft tops put the Red Bull leader in first place with a 1m16.622s.
It looked like Verstappen would retain the lead in FP1 – after sweeping practice in the season opener last time in Bahrain – but the Black Arrows riders went for one last race and demoted him to third rank.
Hamilton’s latest flyer initially put him back in first place before Bottas, who won pole for F1’s visit to Imola in 2020, overtook him by 0.041s with a 1m16.564s.
Charles Leclerc missed much of the race in the first half of the session as Ferrari investigated a problem with his car, but had a good lap late to take fourth and leave Gasly in fifth.
Sainz eventually finished sixth ahead of Fernando Alonso and Lance Stroll, with Nicholas Latifi – who fled into the gravel after taking an oversteer slap as he exited Rivazza’s first corner after the session restarted – ninth for Williams ahead of McLaren driver Daniel Ricciardo.
Perez and Ocon finished 16th and 17th in the final standings as their clash ended their respective races.
A second red flag came out after the checkered flag was waved after Nikita Mazepin came out of the second turn at Rivazza – the last actual turn on the track – and hit the front left part of his front wing against the wall near the entrance to the pit lane. .
In the same spot where he had twisted the first few laps of the session, the Haas pilot dipped his right side wheels onto the curb and gravel, causing him to twist and knock him against the wall.
F1 Emilia Romagna GP – FP1 Results