Lewis Hamilton was fastest in FP1 for the United States Grand Prix as Mercedes enjoyed an advantage of nearly two seconds over the rest of the field.
The defending champion was 0.3s clear of championship leader Nico Rosberg in the opening session as both Mercedes drivers improved by a second on the soft tyre having completed early running on the supersofts. The margin between Hamilton and Max Verstappen in third place was 1.951s, although both Red Bulls only used the medium compound tyre.
Ferrari also used the soft tyre and Kimi Raikkonen was fourth quickest, just 0.028s slower than Verstappen. On more than one occasion this season, Mercedes has enjoyed a large advantage over its rivals in FP1 before the gap closes throughout the weekend, but it was an ominous start from the constructors' champions.
Nico Hulkenberg was fifth quickest for Force India, less than 0.1s ahead of Valtteri Bottas for Williams. Both drivers set their times on soft tyres after running the Halo at the start of the session, with Bottas testing a white version of the cockpit protection device in order to blend in with the Williams livery.
Daniel Ricciardo was seventh on the medium tyre, just ahead of former Red Bull team-mate Sebastian Vettel in eighth. Vettel ran wide at Turn 19 - the penultimate corner - with 25 minutes of the session remaining and damaged his car on the kerb, with a piece of bodywork breaking his right hand wing mirror, which Vettel then held on to for a full lap before pitting.
Vettel wasn't the only driver to have an off-track moment, with Daniil Kvyat - who also ran the Halo - spinning at Turn 18, while Jolyon Palmer also had a spin at the same corner. Palmer later blocked Vettel at Turn 8 to receive a gesture from the German. Kvyat ended the session ninth fastest with Carlos Sainz also in the top ten, but the two Toro Rossos set their best times on supersoft tyres.
It was a tricky first session in front of home fans for Haas, with Romain Grosjean 14th, just ahead of team-mate Esteban Gutierrez. After Grosjean lost a piece of bodywork over the kerbs of the high-speed corners in the first sector, Gutierrez ran over the debris a few moments later. Both drivers then stopped at the end of the pit lane late in the session, line astern, and had to be recovered by the Haas mechanics.
Another driver to struggle during the session was Jenson Button, who limped back to the pits late on to bring his session to a slightly premature end in 18th place.
Button ended the session 0.2s adrift of Alfonso Celis driving for Force India in FP1, while there was a Friday practice debutant in the form of Jordan King for Manor. King had a solid session ending up 20th overall, splitting the two Renaults and nearly two seconds quicker than team-mate Esteban Ocon, although he ran softs compared to medium tyres for all those around him.
|03||Max Verstappen||Red Bull||1:39.379||28|
|05||Nico Hulkenberg||Force India||1:39.712||27|
|07||Daniel Ricciardo||Red Bull||1:39.963||26|
|09||Daniil Kvyat||Toro Rosso||1:40.131||16|
|10||Carlos Sainz||Toro Rosso||1:10.140||26|
|17||Alfonso Celis||Force India||1:41.422||27|