Ferrari Formula 1 driver Charles Leclerc set the fastest time in first practice for the United States Grand Prix at the Circuit of the Americas ahead of Red Bull's Max Verstappen.
The session had the feel of a pre-season test as the condensed sprint race schedule at Singapore and a week off before this race, after a triple-header, meant the teams put the more-traditional-three-practice weekend schedule to work immediately.
No matter the tyre or run, Leclerc repeatedly pumped in fastest times across the session and headed F1's form driver Verstappen by 0.084s.
It was an unusual session whereby we had to wait until later on to see true, comparable pace from leading teams because they initially split tyre strategies.
Ferrari and McLaren dominated the early running on mediums while Mercedes and Red Bull tried the hards and ran roughly in that order, before they converged later in the session as all teams picked up the soft tyres to try.
Once on the softs, Lando Norris showed well for McLaren as he beat the two Mercedes and Lewis Hamilton's Ferrari to take third, with his team-mate Oscar Piastri over three tenths down in seventh.
George Russell managed fourth ahead of Mercedes team-mate Kimi Antonelli.
It was an eventful session as Mercedes ran a new front wing, Russell having had a front-wing issue early on that caused understeer, while he also later flat-spotted a set of hards, which meant a change of plan that kept Russell on hards and swapped Antonelli to softs.
That confused Antonelli, who had clearly been told he was due to take a set of hards late-on.
Hamilton's sixth place masked his pace as he went really wide at Turn 1 around the time that Leclerc set the session's best lap, and later Hamilton had another soft-tyre lap scrubbed off for track limits.
Behind Hamilton and Piastri, Gabriel Bortoleto (due to serve a 20-place grid penalty this weekend) was eighth for Audi at the head of the midfield, having started the session with a huge aero rake attached to his car. Cadillac had an even bigger, more ridiculous-looking gate-like device fitted as well.
Arvid Lindblad - facing a five-place grid penalty for taking a sixth internal combustion engine - and Liam Lawson completed the top 10 for Racing Bulls.
Ollie Bearman was 11th for Haas ahead of both Aston Martins, led by Fernando Alonso. He was an impressive - by Aston Martin's 2026 standards, anyway - 1.636s off top spot.
Isack Hadjar was all the way down in 14th for Red Bull, having set his best time on the hard compound.
Williams had an unusual session. Alex Albon managed 17 laps without setting a competitive laptime as he and Carlos Sainz completed runplans of coming out and pitting almost immediately again afterwards.
Colton Herta was the sole 'rookie' FP1 stand-in for this session at his home grand prix. He was 21st and slowest of those who set a representative time, 0.926s behind team-mate Valtteri Bottas ahead, but clearly carrying out development work.
FP1 times
1 Charles Leclerc (Ferrari) 1m36.052s
2 Max Verstappen (Red Bull) +0.084s
3 Lando Norris (McLaren) +0.245s
4 George Russell (Mercedes) +0.326s
5 Kimi Antonelli (Mercedes) +0.481s
6 Lewis Hamilton (Ferrari) +0.503s
7 Oscar Piastri (McLaren) +0.734s
8 Gabriel Bortoleto (Audi) +0.943s
9 Arvid Lindblad (Racing Bulls) +1.011s
10 Liam Lawson (Racing Bulls) +1.257s
11 Ollie Bearman (Haas) +1.613s
12 Fernando Alonso (Aston Martin) +1.636s
13 Lance Stroll (Aston Martin) +1.731s
14 Isack Hadjar (Red Bull) +1.738s
15 Pierre Gasly (Alpine) +1.749s
16 Esteban Ocon (Haas) +1.844s
17 Franco Colapinto (Alpine) +2.069s
18 Nico Hulkenberg (Audi) +2.070s
19 Carlos Sainz (Williams) +2.794s
20 Valtteri Bottas (Cadillac) +3.001s
21 Colton Herta (Cadillac) +3.927s
22 Alex Albon (Williams) +31.812s