Ahead of today's opening practice session, the air temperature is 14 degrees C, while the track temperature is 26 degrees. It is bright and sunny, though somewhat cool.

There are a number of reserve drivers on duty this morning, Antonio Giovinazzi at Haas, Charles Leclerc at Sauber, Sean Gelael at Toro Rosso and Alfonso Celis at Force India giving the Pink Panthers an all-Mexican line-up for this session.

Vandoorne, who along with teammate Alonso will start the race from the back of the grid (again), is running the Halo at the start of this session. At Toro Rosso Hartley is also running the device.

The McLaren pair head the queue at the end of the pitlane, and as the lights go green they head out, followed by Ricciardo, Celis, Gelael and Vettel. Verstappen is another early riser.

The drivers sport a mixture of all three compounds, all a step softer than last year.

While the title is done and dusted, and Mercedes continues to big-up its underdog role, Ferrari will desperately want to end the season on a high.

The installation laps complete, the drivers head back to their garages. While most have completed just one lap, a couple stay out for two. Just six minutes into the session, all have made an appearance.

Giovinazzi posts the first time of the weekend, the Italian stopping the clock at 1:27.318. He subsequently improves to 24.350 then 23.841.

Ricciardo's Red Bull sports the now traditions FP1 garden gate.

Bottas looks likely to be the second driver to post a time, and it should be markedly quicker than that of the Sauber. Indeed, the Finn crosses the line at 21.212.

Stroll, however, can only manage 28.800.

Still warming his tyres, Hamilton runs wide and over the4 grass at T2. The world champion elect subsequently posts 26.364.

Bottas improves to 20.584.

Local hero Perez goes second (20.685), ahead of an improves Hamilton (21.013), Stroll and Hulkenberg.

Bottas raises the bar, slightly, with a 20.354.

As Vettel begins his first flying lap, Hamilton posts 19.815, the guy is serious.

Vettel posts 21.407 to fourth but is instantly demoted by Massa as Bottas takes the top spot with a 19.614.

Wehrlein takes a very, very bumpy ride over the kerbs as Hartley has a big slide in T2. While only his second GP weekend, the Kiwis was a winner here earlier in the year in WEC.

The Bulls, led by Ricciardo, go fifth and sixth, leaving Vandoorne, Raikkonen and Magnussen as the only drivers still to post a time.

Vettel splits the Mercedes duo with a 19.685, just 0.021s off Bottas' pace, only to be demoted when Verstappen bangs in a 19.551.

Thirty minutes into the session, all but Vandoorne are on track.

The order continues to change as Hamilton now goes quickest, the Briton crossing the line at 19.373. Raikkonen posts 20.459 to go 8th.

"Slow down and box," Magnussen is told. "We're losing water."

The VSC is deployed when Hartley comes to a halt in the escape road at T4.

"Engine stopped," warns the Kiwi. However, moments later he reports the engine is OK and he gets going again. "I'm moving, can I continue," he asks. "Yes," comes the reply.

As Raikkonen goes second (19.375), the leading three have set their times on supersofts, while fourth-placed Verstappen is on softs. The highest runner on ultrasofts is 8th placed Massa.

A 19.041 sees Vettel go quickest and as the German goes purple in S1 it looks likely that we're about to see another corker. Indeed, the Ferrari driver posts 18.824 despite losing pace in S3.

As the drivers head back to their garages, at which point the extra set of tyres is handed back, it's: Vettel, Bottas, Verstappen, Hamilton, Raikkonen, Perez, Ricciardo, Massa, Alonso and Sainz. Vandoorne still to post a time.

"So that's half of FP1 over and we have three different teams (and two different tyre compounds) in the top three," says Pirelli. "So far."

Following several minutes of inactivity, Bottas breaks the silence and heads out... on the ultrasofts.

On the purple-banded rubber Bottas raises the bar with a 17.824, exactly one second quicker than Vettel's best on the supersofts.

Hulkenberg, and Hamilton head out on ultras, while Raikkonen sticks with the supers.

As work continues on Vandoorne's car, it is revealed that the new engine which has consigned him to the back of the grid, appears to have an issue and consequently another engine is required.

Hamilton goes second with an 18.613, albeit 0.789s off his teammate's pace.

Hulkenberg goes sixth with a 19.552, the Renault looking a real handful.

Gelael asks if there is something wrong with the recharger. He is told that it is on and not to worry about it.

On the ultras, Hamilton is strong in S1 but losing time in the final two sectors.

A spin for Gelael at T6.

Verstappen, still on supers, improves to third with an 18.395.

No sooner has Raikkonen spun at T6 than Celis hits the barriers at T16 causing the session to be red flagged.

"I crashed," he reveals. Asked if he can drive it back to the pits he admits that it is too badly damaged.

Replay shows he lost it over running over the kerbs, the rear end snapping out.

"I think there's a lot of damage," admits Celis, as a forlorn Ocon watches on the monitor.

All of which means that as the clock continues to count down, drivers are missing out on their longer runs.

Race control confirms the session will resume at 11:07, leaving 23 minutes of running.

Vettel leads the way as the session resumes, and in the Red Bull there's drama as Verstappen's car is raised on to its stand amidst talk of an engine issue. However, Christian Horner insists it's a "set up" issue and "not serious", even though the youngster won't be going out again.

Perez is quick to improve to 8th (19.440), just one place behind Alonso.

Though Mercedes is currently dominating the timesheets, we've yet to see the Ferraris or Red Bulls on the ultrasoft rubber. And with those "set up" issues, we won't be seeing Verstappen on the purple-banded tyres this session.

Check out our Friday gallery from Mexico, here.