Ferrari are not running a rookie in this session, so regular drivers both Lewis Hamilton and Charles are both out on track.

The seven-time world champion is only a point behind George Russell in the fight for second in the standings, and now he's gone above team-mate Leclerc by 0.060 seconds with a time of 1:19.137 on the hard tyre.

The stewards are going to investigate Audi leaving a cooling fan on Freddie Slater's car after the session, and now it looks like the teenager's practice running is over.

The highest rookie of the 10 that are out on track in Mexico is Red Bull's Ayumu Iwasa, who was third on the timesheets before Lewis Hamilton clocked a marker a couple of tenths quicker. But fourth is still good for 25-year-old Japanese driver.

Meanwhile, fellow rookie Freddie Slater is down at the bottom of board, and now the Briton has to come into the pit lane, as he has a cooling fan still attached to his Audi.

Marc Priestley
Ex-F1 mechanic on Radio 5 Sports Extra in Mexico City

This is what this session is - and it's going to hamper the drivers not in the car.

The likes of Verstappen and co, although he'll get up to speed very quickly, but there is so much unknown going into the weekend with these 2026 cars.

It's a huge learning from everybody.

Nikola Tsolov is only seven points off incoming Haas driver Rafael Camara in the Formula 2 standings, and the 21-year-old Bulgarian has been spoken about as a potential replacement for Liam Lawson at Racing Bulls next season.

This is Tsolov's first F1 practice session, and he's not doing too badly with a time of 1:20.661, placing him eighth behind Nico Hulkenberg and ahead of McLaren Oscar Piastri.

Australian Piastri, meanwhile, has just had a moment on his medium tyres.

Image source, FIA

Ferrari, Red Bull and McLaren are among the teams to bring upgrades to the Autodromo Hermanos Rodriguez, but most of the modifcations are small, circuit-specific tweaks for the weekend - nothing major.

Red Bull

Engine cover, sidepod.

Ferrari

Engine cover, cooling louvres.

Racing Bulls

Coke/engine cover, cooling louvres.

McLaren

Colling louvres.

Alpine

Exhaust tailpipe.

Audi

Rear corner.

It looks like Isack Hadjar will be stuck in the garage for a little while, as his Red Bull has a power-unit issue. Team-mate and four-time world champion Max Verstappen has made way for Ayumu Iwasa in this opening practice session, who sits ninth on the timesheets.

Leonardo Fornaroli is taking reigning world champion Lando Norris' car out for a spin, but the Italian has a big twitch at Turn 11, and asks his McLaren pit wall to take a look.

Charles Leclerc was told Ferrari have been picked as favourites for this weekend's Mexico City Grand Prix. "And who are the people?!" he joked in reply. The Monegasque driver was on the podium in Austin last week but he said Mercedes are still the team to beat no matter what track they go to this season.

Just like in Texas, Leclerc is leading the practice session with a time of 1:19.197 on the hard tyre.

Championship leader Kimi Antonelli manages to make a lap stick and goes top of the timesheets with a 1:20.155 on the hard C3 compound.

Nico Hulkenberg in the Audi is four tenths off the Italian in second, with Racing Bulls rookie Arvid Lindblad, who has F2 driver Nikola Tsolov as a team-mate for FP1, third quickest on the board.

Will Oliver Bearman be driving for Haas next season? More than likely. But the British driver still hasn't been confirmed alongside new rookie Rafael Camara. He goes to the top of the leader briefly in Mexico but like Kimi Antonelli before him, his best lap time is deleted for track limits.

Over at Red Bull, Isack Hadjar's troubles continue. The Frenchman had a lot to say over the radio in Austin and now he's got issues again. "Something wrong man. I have no power. What's happening?" he asks his pit wall.

The route to success is pretty simple for Kimi Antonelli.

To overtake Sebastian Vettel in the record books as the youngest F1 world champion (Vettel was 23 when he won his first champoinship in 2010), Antonelli can...

• Finish ninth if George Russell wins the race
• Finish 10th if Lewis Hamilton was to triumph on Sunday
• If neither Russell nor Hamilton seal victory in Mexico, the Italian will be title winner wherever he finishes in Mexico.

The timing tower has some unfamiliar names on it for first practice in Mexico City, and one to keep an eye on is 18-year-old Briton Freddie Slater, who sitting in fo Gabriel Bortoleto over at Audi and making his Formula 1 debut.

Kimi Antonelli is out early on a very busy track but th Italian is quite wild in the final sector, and his fastest lap time on the hard tyre ends up in the bin.

Marc Priestley
Ex-F1 mechanic on Radio 5 Sports Extra in Mexico City

It's really looking like this weekend is when it'll be done for Antonelli. It means all the talking will be over - and it'll be great to get that out of the way - but there's a lot to be decided still.

The fight for second place looks tight, while there's the constructors' title too.

Pirelli has selected the softest tyres in the range for this weekend's Mexico City Grand Prix, with the C3 as the hard - last year the C2 was chosen - the C4 as the medium and the C5 as the soft compound.

The 4.304km circuit has been updated for this year's race, with significant resurfacing from Turn 16 to Turn One and the stretch from Turn Seven to Turn 16, with only the first sector largely unchanged.

The track is usually quite dusty during the opening practice sessions, with the grip improving as the laps tick by. But in its preview, Pirelli says evolution "could be even more pronounced" given the extensive resurfacing work.

Image source, Getty Images

The champion in waiting looks ready to get in the car today after missing yesterday's media duties with illness.

First practice is green.

BBC Sounds

Harry Benjamin, Jennie Gow, former McLaren mechanic Marc Priestley and F1 correspondent Andrew Benson are going to take through Friday's two practice sessions.

To tune in, you can either click the listen live tab at the top of the live page, search for 5 Sports Extra via the BBC Sounds app if you need to go out tonight, or you can ask your smart speaker to "play 5 Sports Extra".

Image source, Getty Images

With the season drawing to a close and teams needing to run a rookie in the car in four practice sessions during the campaign, this opening hour in Mexico City sees 10 teams changing drivers.

There are two new rookies to look out for on track: Bulgarian Nikola Tsolov, who is second in the Formula 2 championship, and 18-year-old Briton Freddie Slater.

Mercedes

Frederik Vesti replaces George Russell

Red Bull

Ayumu Iwasa replaces Max Verstappen

McLaren

Leonardo Fornaroli replaces Lando Norris

Racing Bulls

Nikola Tsolov replaces Liam Lawson

Alpine

Gabriele Mini replaces Franco Colapinto

Haas

Ryo Hirakawa replaces Esteban Ocon

Audi

Freddie Slater replaces Gabriel Bortoleto

Williams

Luke Browning replaces Alex Albon

Aston Martin

Jak Crawford replaces Lance Stroll

Cadillac

Colton Herta replaces Valtteri Bottas

Image source, Getty Images

Max Verstappen's sixth consecutive podium finish at the United States Grand Prix has helped Red Bull leapfrog McLaren - although the two teams are level on points - and into third place in the constructors' championship.

Leaders Mercedes are ahead of second-placed Ferrari by 133 points, while Racing Bulls have pulled away from sixth-placed Alpine by 33 points in the battle to finish fifth this season.

Image source, Getty Images

With a gap of 123 points to nearest challenger George Russell, Kimi Antonelli has one hand on the trophy as we head into the Mexico City weekend.

Either Mercedes' team-mate Russell and Ferrari's Lewis Hamilton, who is 124 points behind Antonelli, have to win the race at the Autodromo Hermanos Rodriguez and hope the Italian finishes outside the points, so the title is really the 20-year-old's to lose on Sunday.

The fight for second place in the drivers' championship, though, is still very much on. Russell has it, but Hamilton, fourth-placed Max Verstappen and Charles Leclerc in fifth are right on his tail, with nine points separating the chasing pack.

Lorraine McKenna
BBC Sport Journalist

Image source, Getty Images

Hello, folks. Formula 1 is preparing to crown a new world champion this weekend, as 20-year-old Kimi Antonelli stands on the brink of wrapping up his maiden drivers' title with races to spare.

The Italian needs only two points from the Mexico City Grand Prix to seal the championship and become the youngest-ever title winner in F1 history. His victory in Austin last week brought him one step closer to glory, and now a finish in the top nine will guarantee the tequila will be flowing in the Mercedes garage on Sunday.

Image source, Getty Images

For George Russell in second and Lewis Hamilton in third in the standings, anything less than a perfect weekend - with Antonelli also faltering - means the championship fight will be over for another year.

Mexico is the second race of this Americas triple-header, so some drivers are starting to feeling a bit under the weather. Championship leader Antonelli and Cadillac's Valtteri Bottas both missed Thursday's media day with illness, but the two drivers should be back in the car today.