Carlos Sainz set the quickest time in the opening practice session for the Formula 1 United States Grand Prix, with Max Verstappen slotting in P2.
In a busy first 60 minutes of practice at the Circuit of the Americas, Ferrari driver Sainz pumped in a 1m:36.857s on the Soft Pirellis to vault up the leaderboard and cement P1.
He briefly knocked Verstappen down to fourth, but the new World Champion came back with a 1m:37.081s effort, but his best effort was still 0.225s behind the benchmark time.
Lewis Hamilton was a strong third for Mercedes, whilst Lance Stroll impressed with fourth place in a strong first session for Aston Martin. The second Red Bull of Sergio Perez rounded out the top five.
Giovinazzi's nightmare return to an F1 session
With the second session scheduled to be a Pirelli tyre test, FP1 was the only time the teams were able to do set-up work on their own terms.
There was early drama as the session was briefly red-flagged for Antonio Giovinazzi's crash.
Subbing in for Kevin Magnussen at Haas, Giovinazzi crashed through the high-speed sweepers in Sector 1, but after the clutch overheated, his session was done not even 10 minutes in.
When the session restarted, Verstappen went P1 with a 1m:37.462s effort on the Soft Pirellis, nearly one second clear of teammate Perez.
On his first flying lap on the Soft tyres, Hamilton jumped up to P2, just one tenth of a second behind Verstappen, having set a purple time in the final sector.
Stroll then briefly went 0.002s clear of Verstappen's time, before Sainz bolted on a fresh set of Softs to post his 1m:36.857s and take P1.
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Fernando Alonso was sixth for Alpine, two tenths behind Perez, with Mercedes' George Russell, and AlphaTauri's Pierre Gasly slotting in behind after late flyers on the red-walled Soft tyres.
The ninth-placed McLaren of Lando Norris was 0.999s slower than former teammate Sainz, as Sebastian Vettel ensured both Aston's were in the top 10, less than a tenth clear of Alpine's Esteban Ocon in 11th.
Zhou Guanyu - who is also taking a five-place grid drop for a fifth ICE - was 12th, ahead of Williams' Alex Albon - the last driver within two seconds of Sainz in 15th.
The final regular drivers were Yuki Tsunoda and Mick Schumacher in 14th and 15th for AlphaTauri and Haas.
Shwartzman fastest of the FP1 rookies
FP1 featured four rookies in place of full-time drivers: Robert Shwartzman (replacing Charles Leclerc at Ferrari), Alex Palou (Daniel Ricciardo, McLaren), Theo Pourchaire (Valtteri Bottas, Alfa Romeo), and Logan Sargeant (Nicholas Latifi, Williams).
It was Ferrari driver Shwartzman who took the honours in 16th, 2.094s slower than Sainz in the sister car, with IndyCar star Palou around one second slower.
Pourchaire and Sargeant were 18th and 19th - with the latter widely rumoured to be announced as a 2023 driver for Williams.
Following his early skirmish with the barrier, Giovinazzi was 20th and last, 6.206s off the pace.
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