Red Bull’s Max Verstappen set the pace in practice at the Miami Grand Prix despite a tricky session punctuated by errors.
The world champion, who ran wide at least three times and complained of braking issues, ended up 0.105 seconds clear of McLaren’s Oscar Piastri.
Ferrari’s Carlos Sainz was third fastest, 0.116secs off the pace.
The Mercedes of George Russell and Lewis Hamilton in fourth and sixth places sandwiched Red Bull’s Sergio Perez.
Both McLaren and Mercedes have significant upgrades on their cars.
Both Mercedes have the full set of new parts, while McLaren have given Lando Norris all their upgrades while Piastri has about half of them.
Norris was down in 16th place after suffering with power-steering issues that meant the steering had a different weight going into left and right-handed corners.
A spokesperson said: “It was (a problem with) asymmetric power steering assistance (that was) not to do with upgrades. We have made some changes during the session to improve it and will fix it after the session.”
Charles Leclerc in the second Ferrari was last in the time sheets. He spun his car out of the tight chicane on to the penultimate straight after just one flying lap.
Leclerc did not hit anything, but he ended up pointing the wrong way at a narrow part of the track. After briefly trying a multi-point turn, he had to sit and wait for other cars, and his clutch overheated.
With his car broadside in the middle of the track, the session was briefly red-flagged to recover the Ferrari and Leclerc’s session was over.
On this sprint weekend, qualifying for the shorter sprint race takes place later on Friday at 16:30 local time (21:30 BST) before the sprint itself at 12:00 (17:00) on Saturday and then grand prix qualifying at 16:00 (21:00).