Lewis Hamilton led the way in the first free practice session of the weekend at the Circuit of the Americas as Mercedes-AMG PETRONAS finished first and second once more.
Hamilton was the only driver to breach the 1:40s barrier, with his best time of 1:39.941s almost three tenths of a second faster than team-mate and championship rival Nico Rosberg.
In a session that started on a damp track but under blue skies, it was the two Mercedes drivers who set the first timed laps, with Rosberg’s 1:50.219s being usurped moments later by Hamilton’s 1:49.164s, before Jenson Button took over at the top for McLaren Mercedes before the Mercedes reassumed their usual position at the top.
Button held on for third ahead of Daniil Kvyat, with the Russian once again showed strong pace for Scuderia Toro Rosso, three weeks after qualifying fifth at his home race at Sochi.
Kevin Magnussen ended the session fifth in the second McLaren ahead of Fernando Alonso in the leading Ferrari, who saw Kimi Raikkonen struggle once more and end the session outside the top ten.
It was also a mixed session for the Infiniti Red Bull Racing duo, with Sebastian Vettel finishing seventh in the session on the day it was confirmed he will take a penalty for taking a sixth power unit, while Daniel Ricciardo missed most of the session after suffering an ERS failure after just five laps.
Two test drivers had a run in the session, with Felipe Nasr replacing Valtteri Bottas at Williams Martini Racing and Max Verstappen in for his second session of the season in place of Jean-Eric Vergne at Toro Rosso, and the duo finished eighth and tenth respectively, with Sahara Force India driver Nico Hulkenberg in between them in ninth.
Hulkenberg was delayed in the pits early in the session with an unspecified issue, while Adrian Sutil and Pastor Maldonado both suffered quick spins but were able to keep going.
Maldonado’s Lotus team-mate Romain Grosjean was the driver chosen by the team to trial the new front wing, which is aimed at next year’s car. With their usual twin-tusk style front wing being outlawed next season as part of a change of regulations, the team took advantage of the session to test the different nose cone at Austin, although Grosjean ended up eighteenth and last with Marussia and Caterham absent, although he was mainly concentrating on aero runs rather than going for outright pace.
Austin Free Practice 1 Times
| Pos | No | Driver | Team | Time/Retired | Gap |
| 1 | 44 | Lewis Hamilton | Mercedes | 1:39.941 | |
| 2 | 6 | Nico Rosberg | Mercedes | 1:40.233 | 0.292 |
| 3 | 22 | Jenson Button | McLaren-Mercedes | 1:40.319 | 0.378 |
| 4 | 26 | Daniil Kvyat | STR-Renault | 1:40.887 | 0.946 |
| 5 | 20 | Kevin Magnussen | McLaren-Mercedes | 1:40.987 | 1.046 |
| 6 | 14 | Fernando Alonso | Ferrari | 1:41.065 | 1.124 |
| 7 | 1 | Sebastian Vettel | Red Bull Racing-Renault | 1:41.463 | 1.522 |
| 8 | 40 | Felipe Nasr | Williams-Mercedes | 1:41.545 | 1.604 |
| 9 | 27 | Nico Hulkenberg | Force India-Mercedes | 1:41.722 | 1.781 |
| 10 | 38 | Max Verstappen | STR-Renault | 1:41.785 | 1.844 |
| 11 | 19 | Felipe Massa | Williams-Mercedes | 1:41.907 | 1.966 |
| 12 | 7 | Kimi Räikkönen | Ferrari | 1:41.965 | 2.024 |
| 13 | 13 | Pastor Maldonado | Lotus-Renault | 1:42.329 | 2.388 |
| 14 | 99 | Adrian Sutil | Sauber-Ferrari | 1:42.333 | 2.392 |
| 15 | 11 | Sergio Perez | Force India-Mercedes | 1:42.359 | 2.418 |
| 16 | 21 | Esteban Gutierrez | Sauber-Ferrari | 1:42.516 | 2.575 |
| 17 | 3 | Daniel Ricciardo | Red Bull Racing-Renault | 1:42.598 | 2.657 |
| 18 | 8 | Romain Grosjean | Lotus-Renault | 1:43.229 | 3.288 |
