World Champion Lewis Hamilton set the quickest time during a final free practice session affected by torrential rain in the United States.
Despite the Circuit of the Americas closing the venue to fans until lunchtime, the FIA began the session on time, albeit prohibiting the use of Intermediate tyres due to the conditions.
With rain set to intensify in the afternoon, the circuit was busy during the opening 35 minutes, in case the times from the session count towards the composition of the grid.
Hamilton set a time of 1:59.517 at the mid-point of the session to finish 0.863s clear of Ferrari’s Sebastian Vettel, who posted his quick time early on.
Vettel twice had off track excursions within the space of a few minutes but was able to return to the pits without damaging his SF15-T.
Nico Hülkenberg was third fastest for Force India, ahead of Williams’ Valtteri Bottas and Toro Rosso rookie Carlos Sainz Jr.
Daniil Kvyat placed sixth, while Kimi Räikkönen trailed Vettel early on before slipping to seventh.
Daniel Ricciardo was the first driver to emerge and placed eighth, while Nico Rosberg suffered a high-speed off at Turn 3 during the preliminary stages of running.
Rosberg swiped the barriers with his front wing but was able to return to the track and go ninth.
Felipe Massa and Sergio Pérez were unable to match their team-mates and placed 10th and 11th, ahead of Lotus pair Romain Grosjean and Pastor Maldonado.
Fernando Alonso was 14th, in front of Marcus Ericsson and Jenson Button.
Will Stevens edged out Manor Marussia team-mate Alexander Rossi, while Felipe Nasr and Max Verstappen completed the runners.