Ahead of today's opening session the air temperature is 17 degrees C, while the track temperature is 21 degrees. It is cool, but bright and sunny.
At Manor Jordan King makes his FP1 debut while Force India has Alfonso Celis on duty. They replace Wehrlein and Perez respectively.
While the fight for the title is the main focus this weekend, there is also a lot of interest in Haas, the first American team to race on home soil since 1986.
Tyre options are medium, soft and supersoft, while the detection point of the first DRS zone is 150m after Turn 10, with the activation point after Turn 11, and the second zone's detection point is after Turn 18, with activation 80m after Turn 20, on the start/finish straight.
The lights go green and Bottas gets things underway, followed by Vettel, Ocon, Gutierrez and Kvyat.
More and more drivers head out on a mixture of all three compounds.
Verstappen heads out, his Red Bull covered in sensors.
Five minutes in, all but Magnussen have made an appearance.
Once Magnussen finally completes an installation lap there are several minutes of total inactivity.
Eventually King breaks the deadlock, the Briton heading out to give the crowd something to look at. The Manor driver goes on to post the first time of the weekend, stopping the clock at 1:47.101.
Moments later, Raikkonen posts a far more sensible 42.738 with Alonso crossing the line at 42.774.
Rosberg is the fifth driver to post a time and the German gives notice of his intentions by banging in a 40.223. Bottas, on softs, compared to Rosberg's supers, posts 41.938 to go second.
Also on supersofts, Hamilton goes quickest with a 39.246.
Verstappen reveals he is hitting the limiter in eighth gear.
Vettel (softs) posts 41.411 to go fourth as teammate Raikkonen improves with a 41.110.
A spin for Palmer at T18.
It's only FP1 but Vettel is already getting frustrated, the German gesticulates at a very slow Palmer.
Hamilton improves to 38.943, 0.478s clear of his teammate, with Vettel now third, 1.045s off the pace. Half-an-hour in and all but Ricciardo have posted times.
Rosberg complains of oversteer at low speed, while Kvyat complains of "lots of sliding". Gutierrez confirms that he has flat-spotted his tyres.
Still sliding, Kvyat says he feels he should pit, but he is told to do another lap.
Verstappen improves to seventh (40.983) om mediums but is demoted when Hulkenberg (supers) posts 40.113 to go fourth and Ricciardo (medium) goes sixth with a 40.802.
Ericsson complains of graining to his front tyres.
After forty minutes, when the teams need to hand back a set of tyres, Hamilton is quickest, ahead of Rosberg, Vettel, Hulkenberg, Raikkonen, Bottas, Ricciardo, Verstappen, Massa and Sainz.
Not the best session thus far for Gutierrez who has only completed 5 laps and is twentieth, 5.6s off the pace.
Once again, silence falls over the circuit.
After several more minutes of inactivity, Button heads out to get the show back underway. On the medium rubber the Briton improves to 11th with a 41.663.
The cameras pick out Adrian Newey in the Red Bull garage.
Alonso (softs) improves to seventh with a 40.362.
On softs, Rosberg goes quickest in S1, maintaining the pace into S2. At the line the German posts 37.743, eclipsing Hamilton's best, set on the supers, by 0.958s.
Hamilton heads out, also on the yellow-banded rubber, as Verstappen (mediums) goes third with a 39.379. While he is quickest in S1, Hamilton loses pace in S2. He subsequently aborts the lap.
Check out our Friday gallery from Austin, here.
Ricciardo, when told off the difference between his time and that of his teammate (0.2s), is told this is probably due to different engine settings.
Raikkonen posts 39.407 to go fourth, as Hamilton goes quickest (37.428), despite only being quickest in the final sector.
On the softs, King improves to 17th with a 42.012.
Kvyat spins at T18, as Sainz gets very out of shape in T18, both Toro Rossos looking very nervous.
Ericsson is heading back to the pits very, very slowly. "Something is not working, no power," he tells his team.
As Rosberg warns of debris on the track, the cameras pick up on Vettel who is driving one handed, his other hand holding on to what is left of his mirror after it detonate after running over the kerbs.
As Vettel heads back to the pits the VSC is deployed so that the debris can be retrieved.
As ever, attention now shifts to longer runs of high fuel, though not before Gutierrez improves to 13th (40.970) on the softs. Teammate Grosjean is currently 17th (41.554), though he subsequently improves to 13th with a 40.826.
At which point the Frenchman gets in the way of Verstappen, who is clearly far from happy. Replay suggests the Haas driver was attempting to avoid some debris.
Indeed, Rosberg is warned of debris between Turns 3, 4 and 5.
As Grosjean complains of torque settings, he finds himself ahead of an irate Verstappen yet again. "What the hell is he doing," asks the Red Bull driver.
"Anything I can do to help," asks Button, as the Briton is told to pit.
With six minutes remaining, the Mercedes duo are in a class of their own, separated by 0.315s, they remain almost 2s ahead of third-placed Verstappen.
The Haas duo wait at the end of the pitlane to perform practice starts, the American team grandstanding until the bitter end.
Sadly, there's a problem with Gutierrez' car and the Mexican has to be trollied out of the way. To make matters worse, Grosjean also has an issue. He too has to be pushed back to his garage.
"I can't engage first gear anymore," moans the Frenchman. "I don't know what the **** is going on."
The session ends, Hamilton is quickest, ahead of Rosberg, Verstappen, Raikkonen, Hulkenberg, Bottas, Ricciardo, Vettel, Kvyat and Sainz.
Massa is eleventh, ahead of Nasr, Alonso, Grosjean, Gutierrez, Ericsson, Celis, Button, Magnussen, King, Palmer and Ocon.
Check out our Friday gallery from Austin, here.