Ahead of today's opening session, the air temperature is 28 degrees C, while the track temperature is 50 degrees. It is bright, sunny and hot.

In terms of upgrades, McLaren has a new Sidepod Inlet, Coke/Engine Cover, Cooling Louvres, Floor Edge, Diffuser, Rear Suspension and Rear Wing. The sidepod inlet has been revised aimed at improved flow conditioning towards the rear of the car for improved aerodynamic performance, while the engine cover and coke line have been revised in conjunction with the new sidepod inlet enhancing the flow conditioning downstream. An alternative sidepod shape is available as an option for the aforementioned bodywork, resulting in a change of resultant aerodynamic properties.

As part of the new bodywork package, the cooling louvre layout and position have been altered for maximum aerodynamic performance at various cooling levels. The flow conditioning changes from the bodywork are utilised by a revised floor edge design, resulting in improved aerodynamic performance, while in conjunction with the floor edge, the diffuser has been revised, aimed at extracting more aerodynamic performance from the new flow topology. The changes in upstream aerodynamic flow conditions incentivise a modification to the rear suspension fairings to maximise aerodynamic performance, while the medium isochronal rear wing has been modified to deploy the flap to an alternative position in straight line mode, resulting in a larger reduction in drag.

Red Bull has a new Floor Body & Diffuser, Sidepod, Cooling louvres, Mirrors and Halo. The realisation of development iterations sees a new floor geometry with subtle changes within the permitted geometry to extract more local load whilst maintaining flow stability. Accompanying the new floor, the sidepod has been revised with a new junction or split line to the floor, to supplement the floor changes yielding more local load. To blend the new sidepod to existing surrounding geometry, the cooling louvres have been revised whilst maintaining the range of cooling levels offered previously. Also accompanying the floor and sidepod, the mirror assembly geometry has been revised to aid the downstream conditioning and supplement the local load increase, while a small change to revise a turning vane on the fairing is to better serve downstream components, the flow stability and therefore load generation.

Other than the much-anticipated new, significantly lighter tub, Williams has a new Floor, Tail, Front Corner, Rear Suspension and Rear Corner. The Grove outfit has modified the forward and outboard regions of the floor to extract more performance both locally and across the main underfloor surfaces, while the revised tail geometry has been introduced to suit the floor update. The new surfaces work together with the new floor to generate increased performance locally around the rear impact structure (RIS).

The forward and rearward regions of the front wheel bodywork have been updated to offer both improved interaction with the front wing and an improved downstream flow field with the rest of the car, while, to suit the new onset flow, the surfaces on the rear suspension have been realigned to offer additional performance in the rear corner. The previously described geometry changes have unlocked a new flow field opportunity in the rear corner and Williams have been able to extract additional performance in this region by retuning these devices.

Racing Bulls have a new Front Wing, Front Corner and Front Suspension. The new front wing geometry helps establish a clean flow field, which leads to improved performance from the components downstream of it, while, working in conjunction with the new front wing, the front corner & suspension updates help manage the flow downstream and around the car, allowing the floor to perform effectively.

Audi has a new Front Wing, Front Wing Endplate, Nose, Front Suspension, Floor Body, Floor leading edge devices, Diffuser, Halo, Coke/Engine Cover, Rear Suspension, Rear Corner, Beam Wing, Rear Wing and Rear Wing Endplate.

A full new front wing is being introduced alongside an updated nose fairing to deliver a better flow to the rest of the car while covering the balance levels of the new package. The front suspension fairings have been revised to complement the revised front wing and nose and support the aerodynamic intent of the new package. A new floor is introduced for this event, all surfaces are new and designed to deliver a consistent load increase.

The revised bodywork and associated cooling options have been introduced to work with the updated package and improve management of the downstream flow structures, while the rear suspension covers and brake duct elements have been revised to complement the updated rear end flow field and improve aerodynamic performance. Finally, the revised rear wing assembly features updated elements designed to operate as part of the overall aerodynamic package.

Cadillac has a new Front Corner, Front Suspension and Diffuser. The front corner geometry has been revised to increase the available brake cooling capacity, whilst maintaining flow quality to the rear of the car, while the front suspension fairing surfaces have been updated to retain compatibility with the updated front corner and brake duct geometry. The profile of the lower shedding edge of the rear diffuser winglet has been updated to increase local aerodynamic load across the operating envelope of the car.

Mercedes, Ferrari, Aston Martin, Haas and Alpine do not have any updates this weekend.

While Audi has the biggest upgrade, attention will be on Williams which is hoping to turn its season around, though Albon didn't seem entirely convinced yesterday.

Having missed the last three races Hadjar is back in the Red Bull, while Lawson returns to RB.

Green light, and Lindblad leads the way, followed by Bortoleto, Bottas, Leclerc, Ocon and Perez. As more drivers emerge, hards are very much the order of the day, though the McLaren pair have opted for mediums.

"Crazy pulling on the brakes," reports Hadjar, "crazy, I nearly went into the wall."

Colapinto is also on the yellow-banded rubber.

"The vibrations on these brakes in unbelievable," reports Piastri. "It's twice as bad as anything I've ever had."

Perez posts a benchmark 52.292, however Verstappen responds with a 49.202.

"Something weird is pulling to the right, even when I am ion the straight," reports Verstappen as Norris goes second with a 49.706 ahead of Leclerc (50.231).

Leclerc goes top with a 49.025, but Verstappen responds with a 46.635 - yes 2.390s faster - and Hadjar goes third.

Russell goes second with a 48.109 as Albon reports that his brakes feel "very strange".

Piastri goes fifth, ahead of Hulkenberg, Hamilton, Lawson and Norris.

As Verstappen looks set to improve, Antonelli posts a 47.375 to go second.

In the pitlane, the right-rear brake on Sainz' Williams is on fire.

Verstappen raises the bar again with a 46.512 as Piastri goes third and Hamilton fourth.

Predictably, Antonelli goes top with a 46.265, 0.247s up on Verstappen, as Leclerc goes third, ahead of Russell and Piastri.

"The engine's broken," claims Hadjar as Hamilton goes fourth with a 46.879.

After 17 minutes, still no times from Lindblad, Bortoleto, Bottas or Gasly, the first two have been running massive aero rakes.

A 46.601 puts Russell third.

Alonso goes eleventh with a 49.160 as Hamilton goes second with a 46.365, 0.100s down on Antonelli.

"Hydraulics," reports Antonelli as he stops at Turn 7 and climbs from his car.

The VSC is deployed as an over eager marshal sprays the car with his extinguisher.

As the VSC is withdrawn, Russell and Colapinto head out on softs, Antonelli having made the switch to the red-banded rubber just before his issue.

Having realised he wasn't going to made the corner, Russell heads down the escape road at Turn 3. Elsewhere a big lock-up for Verstappen.

Sainz is back on track as Bortoleto causes a brief yellow flag.

Having checked his car for a suspected issue, Piastri is given the all-clear.

The track is very dusty and there is a fear that fallen leaves are getting into the cars' sidepods.

Verstappen goes top with a 45.787 as Russell goes second (46.261).

Hulkenberg goes sixth (46.871) courtesy of a tow from his Audi teammate.

Like Antonelli, Hadjar's session appears to be over, his car up on its stand in the Red Bull garage.

A 45.387 puts Russell top, as Gasly goes ninth on the hards.

The Ferrari pair are on mediums and are currently fourth (Hamilton) and fifth.

Piastri appears to have an issue, his car has been switched off and pushed into its garage, while the shutters go up on Norris's side of the garage.

Alonso, who gave Russell a highly welcome tow on his fast lap, takes to the escape road at Turn 1.

On the mediums, Lawson improves but remains sixth.

Also on the yellow-banded rubber, Leclerc goes third with a 45.791, 0.404s off Russell's pace.

Ocon improves to seventh with a 46.624, ahead of Lindblad and Hulkenberg.

Bortoleto goes 14th with a 47.151 as Norris heads out, the 2025 world champion having suffered a loose bargeboard.

Lindblad has stopped on track, with Hulkenberg following suit moments later. The driver tracker has frozen so we don't know at which corners.

While Lindblad gets going again, Hulkenberg climbs from his car, his session over.

And now Ocon has stopped at the pitlane exit. However, following some advice from Laura Muller, he is eventually able to get going again.

Bortoleto goes ninth courtesy of a tow from Colapinto, as Piastri heads out and immediately improves to sixth.

So, Russell is quickest, ahead of Verstappen, Leclerc, Hamilton, Antonelli, Piastri, Lawson, Lindblad, Ocon and Bortoleto.

Hulkenberg is eleventh, ahead of Sainz, Albon, Norris, Bearman, Gasly, Perez, Colapinto, Alonso, Hadjar, Stroll and Bottas.

The morning was not without its issues, other than lock-ups and much use of the escape roads, both McLarens had problems, as did Hulkenberg, Hadjar and, of course, championship leader, Antonelli. Then, of course, there was Williams, one of several teams to suffer brake issues.

On the other hand, we are already seeing that, much like Monza, slipstreaming is going to add another dynamic, especially in qualifying.

Check out our Thursday gallery from Baku here.