Ahead of today's opening session, the air temperature is 22 degrees C, while the track temperature is 29 degrees. It is bright but with a fair amount of cloud and a 20% chance of rain.

Having dominated both of yesterday's sessions, Lewis Hamilton was dealt a cruel blow last night when Mercedes opted to change the gearbox on his car having discovered an issue following the Baku race. The German team was quick to point out that it had nothing to do with the infamous clash with Sebastian Vettel.

Nonetheless, the Briton still picks up a five-place grid penalty.

Meanwhile, after a number of drivers incurred damage to the undersides of their cars on the kerbs at Turns 9 and 10 yesterday, said kerbs have been modified overnight.

As was the case in Baku, almost every single driver appeared to have an off or spin at some point or another at almost every single corner.

A number of drivers had a difficult opening day, not least the hapless Jolyon Palmer who missed much of FP2 with an electrics issue.

While Hamilton was quickest, Sebastian Vettel was very much in the mix, as was Valtteri Bottas, while the Red Bulls were also very close, though both drivers lost track-time in FP2 due to "issues".

Also looking strong in both sessions was McLaren, both drivers appearing to benefit from the latest upgrade from Honda, the 'Spec 3'. However, in a worrying, late move it is confirmed that Alonso has reverted to the 'Spec 2' unit for the remainder of the weekend.

"Last night Honda detected an issue with Fernando's MGU-H, so they changed his PU," a McLaren source tells us. "All newly fitted components have been used during previous grands prix so there will be no penalties. The ICE will be Spec 2 from day two in Azerbaijan."

The Haas duo get things underway when the lights go green, Romain Grosjean one of the drivers to incur damage on the kerbs yesterday.

Vandoorne, Hamilton and Raikkonen head out on softs, while Sainz is on the ultras. However, at the end of his installation lap the Spaniard grinds to a halt. "Engine, engine," he tells the team.

As yellow flags are waved, Sainz remains in his car, eventually he is told to try and start the car having previously been told to keep his ignition on. When nothing happens he is told to park the car.

Ass Sainz' car is pushed to safety, Palmer and Ricciardo lead the way as the session resumes, a healthy mixture of all three compounds.

In no time at all there are a host of times on the board, with Verstappen (6.387) leading the way, ahead of Ricciardo, Kvyat and Palmer. All four on ultras.

Advised to mind his tyre temperatures, Verstappen improves to 6.082.

No installation laps for Alonso who gets straight down to it, posting a 6.843 to go fifth.

Verstappen consolidates his top spot with a 6.015.

After 16 minutes just 10 drivers have posted times.

"Main thing we learned yesterday was that performance gaps between the compounds are quite small," says Pirelli. "Which opens up a few different strategy choices."

The Mercedes duo head out and shortly after they are joined by the Ferraris.

Hamilton's first lap is a very conservative 18.335, while Bottas posts 6.555. The Briton subsequently improves to 7.734 while his teammate goes third with a 6.303.

On his first flying lap Vettel goes second (6.036), just 0.021s down on Verstappen, the German quickest in S3.

It's the same for everyone, but Hamilton, in particular, appears to be struggling with traffic. Nonetheless, as his teammate posts 5.726 to go quickest, the Briton responds with a 5.929.

A 5.384 - the quickest lap of the weekend - sees Vettel take the top spot as teammate Raikkonen goes fifth with a 6.038.

Most drivers are on the ultrasofts now, the exceptions being Magnussen, Grosjean, Ericsson and Wehrlein.

Despite PBs in the final two sectors, Hulkenberg can only manage 16th (7.303), though he could be on high fuel, certainly his teammate's pace (6.595) is encouraging.

"I don't know what he is doing," says Raikkonen of fellow Scandi, Magnussen, "he is trying to block me all the time."

"A lot of car vibrations," complains Kvyat, as evidenced by his very shaky voice. They're certainly not good vibrations.

With 22 minutes remaining, there are just a few cars on track, Verstappen, Ocon and Perez.

They are joined by Sainz whose issue has clearly been resolved indeed, The Spaniard subsequently posts 6.719 to go tenth.

Despite complaining of oversteer at a number of corners, Sainz improves to seventh with a 6.405.

Vettel goes quickest in S1 but loses pace in S2 and again in S3. Moments later, Hamilton bangs in a 5.361 to take the top spot.

Check out our Saturday gallery from Spielberg, here.