Ahead of today's opening practice session, the air temperature is 24 degrees C, while the track temperature is 42 degrees. It is bright and sunny. Nonetheless, there is a 20% chance of rain.

In terms of upgrades, McLaren has a new Rear Wing. A small revision to the rear wing endplate will result in improved flow conditioning and aerodynamic characteristics across the full operating range, while the new rear wing assembly has been specifically designed for the increased isochronal of this circuit, resulting in an efficient reduction of drag in straight line and cornering mode.

Mercedes has a new Rear Wing, Rear Corner and Front Wing Endplate. The upper wing element camber has been reduced to drop local downforce and drag at a level appropriate for Spa, while the rear drum winglets position and span have been optimised around evolving onset flow and local load requirements, thus improving robustness through the operating envelope. The endplate top edge camber has been increased to improve front wing performance throughout the operating envelope, improving onset flow to the rear of the car.

Red Bull has reverted to its original rear wing with revised pylon profiles, given that the pylons now by regulation contact the mainplane underside, the interface is sensitive and revised with pylon changes to existing element profiles seeking to extract more load and at least maintain flow stability.

Williams has a new Rear Corner and Floor Body. To suit the demands of the circuit, the Grove outfit has reduced the loading on the rear corner which offers a local efficiency improvement. A further circuit specific change, alters the balance between downforce and drag at the rear of the main floor, while to change the distribution of diffuser expansion volume across the car operating envelope, a new floor body surface has been introduced.

Racing Bulls have a new Coke/Engine Cover, Roll Hoop, Front Corner and Rear Wing. The profile of the sidepods on the engine cover has been modified to provide better control of the airflow passing around the side of the car, while a narrower roll hoop has been introduced, which improves the flow quality reaching the back of the car and on to the rear wing. Detail changes on the front brake drum components bring improvements in air flow management at the front of the car, while a number of changes to the mainplane and flap profiles allow the rear wing to generate downforce more efficiently, bringing performance improvement here and at other circuits.

Haas has a new Front Wing, Front Wing Endplate, Front Corner and Beam Wing. A revised front wing geometry has been introduced to increase local aerodynamic load while maintaining aerodynamic efficiency, improving airflow management and overall front-end performance across a range of operating conditions. Also, a revised front wing endplate geometry has been introduced to complement the updated front wing profiles, optimising local airflow control and maintaining aerodynamic efficiency across the front wing assembly. A circuit-specific front corner configuration has been made available, providing additional flexibility to better match the aerodynamic load requirements of this circuit, while a new lower rear wing configuration has been introduced as a circuit-specific option, providing additional flexibility to align the car's aerodynamic characteristics with the demands of this venue and optimise overall performance.

Audi has a new Rear Wing and Diffuser. The circuit-specific rear wing assembly has been introduced to align the aerodynamic configuration with the requirements of the event, while a minor refinement has been made to the diffuser as part of the ongoing aerodynamic development programme. The update is intended to enhance the aerodynamic behaviour of the surrounding flow field.

Alpine has a new Halo featuring a reprofiled fairing with an additional winglet. The halo has been redesigned to improve downstream flow management and provide aerodynamic load towards the rear end of the car.

Cadillac has a new Front Wing Endplate whose geometry improves flow quality to the forward floor, thereby increasing the aerodynamic load generated in this area throughout the operating ride height range.

There is one reserve driver on duty this morning, Jak Crawford, who replaces Fernando Alonso at Aston Martin.

Green light, and Perez leads the way, followed by Sainz, Albon, Russell and Lindblad.

As previously reported, Norris has a 10-place grid penalty for Sunday after taking on a fourth control electronics unit.

As more drivers emerge, most are on hards, though a few are on mediums, and Hadjar is on softs.

Gasly complains that his steering feels light.

Russell posts a benchmark 50.654, but Hamilton responds with a 50.438 and Verstappen a 49.307.

On the softs, Hadjar stops the clock at 48.918. It's thought the Frenchman will take on a new engine this weekend and will therefore start from the back of the grid.

Fun and games at Williams where Albon is given his teammate's front wing, while Sainz is given a spare.

Leclerc goes third with a 49.887, ahead of Lawson, Antonelli, Hamilton and Russell.

Verstappen improves with a 48.237, 0.227s up on his teammate's pace, albeit on the mediums.

Hamilton goes third (48.842) and Leclerc fourth (48.969).

After 11 minutes, all bar Norris have posted a time.

Verstappen consolidates his top spot with a 47.859, but Hadjar responds with a 47.778.

On successive laps Antonelli runs wide in Turn 19. Albon, Sainz and Bearman have also had times deleted.

"Sainz, what an idiot," declares Antonelli after being impeded by the Spaniard.

With 35 minutes remaining, Antonelli switches to the softs, his teammate subsequently follows suit.

Elsewhere, Norris has completed a number of single-lap runs.

Sainz has been noted for crossing the line at the pit entry.

Antonelli crosses the line at 47.603, the Italian only quickest in the opening sector.

Russell, who is also only quickest in S1, goes fourth with a 47.959 as more drivers switch to the red-banded rubber.

No sooner has Hadjar posted a 47.322 than his teammate responds with a 47.070.

Lindblad is currently seventh, ahead of Bortoleto, Lawson and Piastri.

Norris finally posts a competitive time, the McLaren driver going ninth with a 48.903.

Along with Norris, Hadjar and Stroll will also face significant grid penalties for taking on new power unit components.

Verstappen and Antonelli switch to the mediums as Leclerc goes third with a 47.490 on the softs.

A 47.215 sees Hamilton go second, 0.145s off Verstappen's pace, while his teammate goes third (again) with a 47.277.

Piastri improves to fifth with a 47.522, as his teammate heads out for his first flying lap of the day on the red-banded rubber.

He goes seventh with a 47.931 following a poor S2, the sector in which the Red Bull is particularly strong.

With ten minutes remaining, and the drivers focussing on longer runs, it's mostly mediums and softs, though Hulkenberg and Gasly have opted for hards.

Stroll, who faces a grid penalty on Sunday, is 5.7s off the pace, while Crawford is 6.7s adrift. Aston Martin faces a tortuous afternoon on Sunday. No wonder Alonso is focussed on the World Cup.

Track limits continue to be an issue, with Antonelli and Verstappen among the latest, while Stroll's nose camera has become detached and is flapping about.

An issue with his car means that Bortoleto's session has come to an early end.

Piastri momentarily stops at Les Combes, bringing out the yellows, before his able to get going again.

"Keep driving slowly," he is told, "we have a hydraulics pressure issue." The Australian is able to make it back to the pits.

The session ends. Verstappen is quickest, ahead of Hamilton, Leclerc, Hadjar, Piastri, Antonelli, Norris, Russell, Lindblad and Bortoleto.

Lawson is eleventh, ahead of Hulkenberg, Bearman, Albon, Colapinto, Ocon, Gasly, Bottas, Perez, Sainz, Stroll and Crawford.

Check out our Friday gallery from Spa here.