To Zarco's credit, his lap was done on a nine-lap-old medium rear. This Honda speed does look genuine.
Johann Zarco takes over top spot briefly, but Marc Marquez moves clear with a 1m37.739s - close to the lap record already!
Marc Marquez moves ahead of his younger brother with a 1m38.184s on a new medium rear tyre.
Strong benchmark from Alex Marquez at this stage of the session. He's 0.299s clear of the field with just under 45 minutes to go.
Lap record of 1m37.683s will almost certainly be under threat when we get to the time attack phase of this session later on.
Quartararo has made his way back to pitlane.
- A.Marquez
- Zarco
- Bagnaia
- Di Giannantonio
- Bezzecchi
- M.Marquez
- Binder
- Mir
- Ogura
- Marini
Alex Marquez improves further at the top of the order with a 1m38.205s.
Fabio Quartararo has stopped at the side of the track with an apparent issue on his Yamaha.
Bagnaia finds a huge chunk of time early on Practice, moving up to second with a 1m38.526s - almost two seconds faster than his FP1 best.
Alex Marquez now goes top with a 1m38.370s on the Gresini-run GP24.
Marc Marquez sets the fastest lap of the day on his third lap of the afternoon with a 1m38.749s on the factory Ducati.
Ai Ogura has a proper rodeo moment on the exit of the final corner. He ran over the kerb on his Aprilia and that unsettled the bike. Big scare but he kept it pointing in the right direction.
First laps come in and it's Brad Binder fastest with a 1m39.528s on the KTM.
Pitlane is open for Practice. Alex Rins is first out on track.
Marc Marquez led FP1 this morning from LCR Honda's Johann Zarco.
Pecco Bagnaia was only 16th, though track conditions were not ideal in the opening session.
Just five minutes to go till the all-important hour-long second session of the day.
As always, the top 10 at the end of this session will advance through to Q2 directly on Saturday.
The preceding Moto2 session has ended under red flags for a crash for Alonso Lopez, but he walked away unscathed - his bike just came to a rest in an unsafe place.
Good evening and welcome back to our live coverage of the 2025 MotoGP Argentina Grand Prix.
Practice is due to get underway in 15 minutes.
That's all from us for now, but keep your eyes fixed on Crash.net for all the latest news from the Argentina paddock.
Practice begins at 6pm GMT.
Read the full FP1 report from the 2025 MotoGP Argentina Grand Prix here
Chequered flag has come out and Marc Marquez ends FP1 fastest of all with a 1m38.937s.
He heads Johann Zarco, Alex Marquez, Franco Morbidelli and Marco Bezzecchi.
Pecco Bagnaia ends the session 16th.
Bagnaia makes a small improvement from 20th to 14th, but not a great start to the weekend.
Big moment for Marquez at Turn 9 but he gets away with it.
Marquez improves to a 1m38.937s. That was the 13th lap on that medium rear tyre too.