Kimi Antonelli runs into trouble as Ferrari threaten Mercedes in Miami

Kimi Antonelli encountered a power unit issue late in the sole practice session for the Miami Grand Prix spearheaded by Ferrari's Charles Leclerc.

F1's youngest championship leader, following back-to-back victories in the last two races in China and Japan, again appeared strong throughout for the most part until it came to the time late on when the majority of the field switched to the soft Pirelli tyres.

Mercedes confirmed it had attempted to troubleshoot an issue with Antonelli's power unit but was unable to fix it in time before the end of the session, leaving him fifth quickest, with his leading time on the hard Pirelli compound.

Ferrari, McLaren and Red Bull at least served notice they are ready to mix it at the front with Mercedes this weekend following the session. Leclerc and Lewis Hamilton finished first and fourth quickest, sandwiching Max Verstappen and Oscar Piastri.

Leclerc on song

Unlike other first practice sessions that run for an hour, the FIA decided ahead of this weekend's event at the Miami International Autodrome that for a trio of reasons the single session in Miami would be extended to 90 minutes.

The first was due to the five-week gap in track action following the cancellation of the Bahrain and Saudi Arabian Grands Prix; the second was in light of the technical changes made to the cars following regulatory tweaks, and the third, on the back of those, the lack of practice time going into a sprint weekend.

The majority of the cars also sported a plethora of aerodynamic updates, notably McLaren, Ferrari and Red Bull. In contrast, the Mercedes W17s included nothing more than a new tailpipe and front corner. The team has opted to wait until the next grand prix in Canada in three weeks' time before showing its hand.

After the opening half-hour of running, Antonelli led the way with a lap of 1:30.079s, two-tenths of a second clear of Leclerc, followed closely by Lando Norris and Verstappen, all on the hard Pirelli tyres, which predominantly proved to be the rubber of choice throughout the session.

At exactly the midway point, Leclerc shifted up a gear, posting a 1:29.855s, leaving Antonelli 0.224s adrift, with Hamilton making it a Ferrari one-three, albeit 0.340s adrift of his team-mate.

With less than 13 minutes remaining, only three drivers had used the soft tyres - Aston Martin duo Fernando Alonso and Lance Stroll, and Cadillac's Valtteri Bottas.

It was George Russell who sparked a late rally on the red-striped rubber, but his lap of 1:30.079s was not enough to depose Leclerc and Antonelli from the top two positions.

Instead, it was Verstappen who initially went quickest with a 1:29.776s, but only briefly as Leclerc soon resumed top spot, ousting the four-time F1 champion by exactly a third of a second.

Both drivers improved on their second runs, Leclerc ultimately topping the timesheet with a 1:29.310s, whilst Verstappen was closer, but still 0.297s down.

A fastest first sector from Hamilton on the initial runs suggested he would beat Leclerc, but traffic in the middle sector proved compromising. Instead, the seven-time champion finished 0.467s adrift, with Piastri also ahead of him by 0.019s. 

Norris, who had followed Hamilton with the leading time in the first sector, was equally unable to capitalise after exceeding track limits at Turn 17. The reigning champion finished 0.898s down, with Russell only sixth quickest, 0.790s off the pace.

Alpine's Pierre Gasly, Isack Hadjar in his Red Bull, and Williams' Carlos Sainz completed the top 10, the latter 1.620s down.

At the rear, Alonso and Stroll, in Aston Martins bereft of any updates, were 19th and last respectively, with Racing Bulls' Arvid Lindblad and Bottas sandwiching the duo.