Lewis Hamilton set the fastest time in the opening practice session for the US Grand Prix, 0.292s faster than Mercedes team-mate and championship rival Nico Rosberg.
McLaren's Jenson Button led the way for the first half of the 90 minute session before the Mercedes drivers both set a quick lap to go one-two. Hamilton had a comfortable buffer over Rosberg and was 0.378s clear of Button in third. There was a half second gap back to Russian Daniil Kvyat in fourth after he set an impressive lap in the Toro Rosso.
With just 18 cars competing this weekend following the collapse of Caterham and Marussia, the session lacked some of the usual track action, although most cars completed roughly 20 laps. Daniel Ricciardo only managed five due to an ERS issue on his Red Bull while Williams reserve driver Felipe Nasr was limited to 15 in order to save mileage on Valtteri Bottas' car.
Several drivers made small mistakes around the circuit, but Adrian Sutil and Pastor Maldonado were the only ones to spin off the track. Both managed to keep their cars out of the barriers and continue on their way as they fought over 13th and 14th place, which will be just above the cut off point for Q2 in Saturday's qualifying session.
Fernando Alonso had a couple of dramatic slides in his Ferrari on his way to sixth place by the end of the session. Meanwhile, team-mate Kimi Raikkonen had an awkward moment at the end of the session when he attempted to pass Romain Grosjean in the pit lane, only to miss his own pit box and come to a stop. He finished the session 12th as Ferrari trialled some new parts for 2015 during the session.
Max Verstappen got his second outing at a grand prix weekend, setting the tenth fastest time roughly 0.9s off Toro Rosso team-mate Kvyat. The 17-year-old will take part in Friday practice sessions at the final two races as well to build his experience ahead of his race debut with the team next season.
Grosjean finished the session at the bottom of the timesheets but was testing the first evolution of Lotus' 2015 nose, which does not feature the distinctive two-pronged design on this year's car.