George Russell was fastest from Mercedes team-mate Kimi Antonelli in the first practice session at the new Madring circuit in Madrid.
Russell is looking to hit back after losing out to championship leader Antonelli last Sunday at Monza and started the Spanish Grand Prix weekend perfectly as he outpaced Antonelli by 0.286s.
But Ferrari were quick early on and were only half a second off the best times on the medium tyres, compared to the Mercedes on the softs.
Charles Leclerc, who is fit enough to race despite suffering from blurred vision in the aftermath of his huge Monza crash, eventually improved on the softs to third but Lewis Hamilton's best time remained on the mediums.
Hamilton was called out by at least four drivers for impeding across the practice hour as the tight confines of the Madring meant traffic was an issue.
Arvid Lindblad first called Hamilton and Antonelli "stupid" for blocking the track at the high-speed banked Turn 12 before Leclerc, Audi's Nico Hulkenberg and Williams' Carlos Sainz all had to abandon flying laps due to the seven-time world champion not being aware of them coming.
Sainz said on the radio of his incident: "Lewis letting by in the middle of Turn 12. It's always the same, it's so dangerous!
"Like it takes zero effort to be two metres more left. Zero effort!"
There were concerns about plenty of disruption in practice after 19 red flags were required in a two-day Formula 3 test last month, but all 22 F1 drivers kept it out of the barriers.
Track evolution was high throughout the session but it already looks like Mercedes and Ferrari are going to contend for top spot this weekend.
"I'm really impressed with the way they approached this brand new circuit," said Your Site F1's Anthony Davidson.
"They made it look easy really - which they often do."
Red Bull's Max Verstappen was fifth ahead of McLaren's Lando Norris, while rookie Lindblad impressed in seventh for Racing Bulls.
Audi had strong pace with Nico Hulkenberg in ninth and Gabriel Bortoleto in 11th with Red Bull's Lawson in 10th.
Friday September 11
2.40pm: Team Bosses' Press Conference
3.45pm: Spanish Grand Prix Practice Two (session starts at 4pm)
5.20pm: F3 Qualifying
6.20pm: The F1 Show
Saturday September 12
10am: F3 Sprint
11am: Spanish Grand Prix Practice Three (session starts at 11.30am)
1.10pm: F2 Sprint
2.15pm: Spanish Grand Prix Qualifying build-up
3pm: SPANISH GRAND PRIX QUALIFYING*
4.55pm: F3 Feature Race 1
6pm: Ted's Qualifying Notebook
Sunday September 13
8.40am: F3 Feature Race 2
10.20am: F2 Feature Race
12.30pm: Grand Prix Sunday: Spanish GP build-up
2pm: THE SPANISH GRAND PRIX
4pm: Chequered Flag: Spanish GP reaction
5pm: Ted's Notebook
*also on Your Site Main Event
Formula 1 is in Madrid for the Spanish Grand Prix at the new Madring circuit with Sunday's race at 2pm (build-up from 12.30pm), live on Your Site F1.
