Kimi Antonelli and George Russell are both running Mercedes' latest-specification car at this weekend's United States Grand Prix, as the team continue to try to get to grips with their long-awaited upgrade package.

At Williams, Carlos Sainz and Alex Albon have each put a time on the board after waiting in the Williams garage. But the pair are down at the bottom of the timesheets, Spaniard Sainz the quicker of the two team-mates.

There is not much difference between George Russell and Kimi Antonelli on the soft tyre, and now Briton Russell has headed out on the hard compound with 12 minutes remaining of the session.

Antonelli has a question for his pit wall, though. "Wasn't I meant to go with the hard?" asks the Italian. Engineer Pete Bonnington replies there has been a change of plan, so the soft compound will be staying on his car for now.

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Kimi Antonelli just got in the way of Isack Hadjar as the Red Bull driver was on a fast lap, so the championship leader holds his hand up to say sorry to the Frenchman. Hadjar is 12th and Antonelli fifth so far in first practice.

Hadjar, Antonelli and Lewis Hamilton have all had lap times deleted for track limits at COTA suring this session, as Charles Leclerc, Max Verstappen and world champion Lando Norris occupy the top three places on the timesheets.

Lewis Hamilton runs wide at Turn 19 on his latest run on the softs, so the seven-time world champion stays sixth on the board, 0.635 seconds off the pace of his Ferrari team-mate Charles Leclerc.

If the update is Ferrari's biggest of the year, it looks to be working for Charles Leclerc. The Monegasque driver pulls out more performance from his car to jump above Max Verstappen's Red Bull by 0.084 seconds. The new time to beat is 1:36.052.

McLaren's Oscar Piastri goes seventh quickest, as Kimi Antonelli in fifth is finding it difficult to keep his Mercedes under control towards the end of the lap.

Rebecca Clancy
F1 journalist on BBC Radio 5 Sports Extra in Austin

The chat in the paddock this morning is that the upgrades that Ferrari have brought are actually far more significant than the drivers have been letting on. Some are even suggesting that it's the biggest upgrade package of the year for Ferrari.

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The drone shot is back for the TV coverage this weekend. It's following Max Verstappen, who is purple in the first sector and has enough pace in the bank to beat Charles Leclerc's top time by 0.192 seconds.

Red Bull team-mate Isack Hadjar has moved up the order on his flying lap on the soft compound, slotting into fifth place with a 1:36.490.

Kimi Antonelli needs to win this weekend and George Russell and Lewis Hamilton to trip up in order to become the youngest ever F1 world champion. The 20-year-old is more than four tenths off Charles Leclerc's best time at the moment, sandwiched between Lando Norris, who was fast in the middle sector, and seven-time world champion Lewis Hamilton.

Charles Leclerc is a past winner in Austin and the Ferrari man is looking quick already. He's switched onto the soft tyre now and his new lap time of 1:36.052 is good enough to keep him at the top of the timesheets.

Max Verstappen is second quickest, 0.084 seconds off the pace of the Monegasque driver on the same soft compound.

The Williams garage is busy on both sides as Carlos Sainz and team-mate Alex Albon wait to set an opening lap time in first practice in Austin. It's been a disappointing season overall for the team, and they sit ninth in the constructors' championship behind the likes of Audi and Haas.

Speaking of Audi, German Nico Hulkenberg says his car has "very weird behaviour in the last corner," at COTA.

1. Charles Leclerc (Ferrari) - 1:36.761

2. Lewis Hamilton (Ferrari) +0.074

3. Lando Norris (McLaren) +0.423

4. Kimi Antonelli (Mercedes) +0.424

5. George Russell (Mercedes) +0.493

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Even Formula 1 drivers get put on the naughty step when they misbehave on track.

Reigning world champion Lando Norris said he had "plenty of telling offs" after his contact with McLaren team-mate Oscar Piastri on the final lap of the sprint event in Singapore last time out. Norris came away with a single point while Australian Piastri was left with a DNF in the shorter race.

After the dressing down, Norris added the pair are still free to race each other over the remaining races, they just can't do anything stupid.

Norris has dropped to sixth in the drivers' championship after his back-to-back victories in Hungary and Zandvoort following the summer break, and in Austin, he's third on the timing screen, four tenths behind leader Charles Leclerc.

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The drivers could be in for a bumpy ride around the Circuit of the Americas this weekend.

Four-time world champion Max Verstappen said on Thursday he loves this track and the layout, and he also loves being in Austin, however, the rough nature of the circuit leaves a lot to be desired.

"For me the bumps are unacceptable. Over time they've been grinding a little bit here and there but it's just putting a plaster on the big problem," said the Dutchman.

"But that of course means you need to really fully open up the track. That costs a lot of money and time but that's the only way to get rid of it because these bumps are not natural and they are out of control."

Lumps and bumps aside, Verstappen is aiming for a third consecutive victory on Sunday following his wins in Singapore and the Bahrain Grand Prix in Malaysia. He;s also made the podium in the past five grands prix, too.

Ferrari have brought some upgrades to the United States Grand Prix as they look to celebrate a first win since Charles Leclerc's victory at Silverstone in the summer.

The Italian team are one and two on the timesheets so far, but it's now Leclerc who is quicker than team-mate Lewis Hamilton by 0.074 seconds on the same medium tyre.

Over at Mercedes, George Russell is telling his pit wall to check the front wing, saying he is experiencing "lots of understeer".

Lewis Hamilton was in reflective mood on Thursday, going over how his strategy error in Singapore cost himself and Ferrari a podium finish at Marina Bay. The seven-time world champion said it was a "split-second decision" to stay out and not pit under the virtual safety car, adding he held his hands up to the team and took responsibility for it.

Can he get back on the podium this weekend? Ferrari have been backed to perform well at COTA, and Hamilton has just put himself top of the timesheets with a 1:36.835 on the medium compound.

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If the steering feels weird, it hasn't affected Max Verstappen's ability to clock a quick lap just yet. The Dutchman jumps to the top of the timesheets with a 1:38.040 but that marker is beaten by the Ferrari of Charles Leclerc.

The Monegasque driver, who is about to become a dad any day now, is eight tenths faster than the Red Bull with a 1:37.430. World champion Lando Norris is next to cross the line and goes within six tenths of Leclerc to slot into second place.

Harry Benjamin
BBC F1 Commentator in Austin

Turn One is so wide, it gets wider as you up the corner and then it pincers you in right at the apex. You can take multiple lines through that corner - it's a prime overtaking spot straight away.

American Colton Herta is in for Sergio Perez over at Cadillac in this first practice session, the only rookie out on track at the moment.

There is a mix of medium and hard tyres on show in the opening stages of this session - and some hefty aero rakes - with Lando Norris quickest so far with a time of 1:38.715.

At Red Bull, Max Verstappen is chatting to his new engineer Tom Hart, who is taking over the radio from Gianpiero Lambiase this weekend. "Steering feels weird, steering left, there is some sort of friction," says the four-time world champion.

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Lewis Hamilton drew laughs in the news conference yesterday when he was asked if he had any advice for Kimi Antonelli. "Slow down!" said the seven-time world champion.

Ferrari's Hamiton then went on to praise the young Italian, adding his performances have been "massively impressive".

Rosanna Tennant
5 Live F1 reporter in Austin

It might only be Friday, it might only be FP1, but the hill is packed out with fans.