Michelin's Piero Taramasso explains that riders are saving their preferred soft tyres for later in the weekend and using harder tyres this morning to clean the track.
Fabio Quartararo, who had a tough time at the February test here, continues his strong start for Yamaha by returning to the top.
At the other end of the timesheets, Iannone has reduced the gap to the top to +3.639s after just 6 laps. Impressive!
Iannone is just 0.069s slower than Aprilia test rider and Trackhouse replacement Lorenzo Savadori.
And now reigning champion Bagnaia moves to the top, by 0.145s from Martin.
...But not for long.
Martin blasts to the top on his 5th lap.
4 laps done and it's now Marco Bezzecchi quickest from Bagnaia and Quartararo.
Title leader Jorge Martin is only 15th at present.
Andrea Iannone is learning the GP23, as well as MotoGP's carbon brakes, Michelin tyres, aero and ride height devices.
The Maniac is +6.350s from the top after 3 laps.
Jack Miller, Fabio Quartararo (who has a new engine this weekend) and Joan Mir lead the timesheets after 2 laps.
Pedro Acosta reaches down and throws something from the seat of his GASGAS machine.
All riders on medium front and hard rear slicks.
Green lights on and FP1 begins.
This morning will also see Andrea Iannone's first MotoGP laps since 2019. The Italian, who served a four-year anti-doping ban before winning a race on his return to racing in WorldSBK this season, is replacing the injured Fabio di Giannantonio at VR46 Ducati.
While this morning's MotoGP session is set to be dry, aside from a few damp patches, more rain is forecast for the afternoon.
Good morning from Sepang in Malaysia where the Moto2 class are in the final stages of their opening practice session.
After earlier rain, conditions are dry, hot and humid.
MotoGP FP1 starts at 10:45 local time, which is in 15-minutes.