Championship leader Sebastian Vettel set the fastest time in the inaugural practice session for this weekend's US Grand Prix at the Circuit of the Americas.
The times tumbled during the 90 session on a slippery track, with Vettel setting his best effort on his final attempt to go 1.418s faster than Lewis Hamilton in second. His championship rival Fernando Alonso was third fastest but 2.212s off the pace as the drivers got to grips with the all-new circuit.
While Vettel's time was undoubtedly impressive, the teams were working through various programmes to get the cars ready for the new track and understand their latest updates. None of the drivers used the medium tyres either, meaning there should be more time to find in the afternoon when the soft tyres go on and track temperatures rise.
Jenson Button was fourth fastest ahead of Mark Webber, Felipe Massa, Nico Hulkenberg and Kamui Kobayashi, who set the pace in the opening stages of the session. Nico Rosberg was ninth fastest as Mercedes focused on back-to-back testing with its two cars, running the latest version of its Coanda exhaust on Michael Schumacher's car and an old-spec exhaust on Rosberg's. By the end of the session Rosberg was 1.4s faster than his team-mate, but it is likely both were sticking to a regimented test programme rather than chasing lap times.
The slippery surface caught out a number of drivers during the session, with Hulkenberg the first man to christen turn one with a genuine spin, before later spinning at turn 13. The penultimate corner also proved to be tricky with most of the field running wide at some point, while both Webber and Heikki Kovalainen lost the rear of their cars at the crest of turn nine later in the session. Turn nine also saw one of the more dramatic moments of the 90 minutes when Hamilton had to take to the grass to avoid the slow-moving Mercedes of Schumacher.
Only HRT chose to run a replacement driver in FP1 as the other teams gave their race drivers maximum track time to learn the new circuit. Ma Qing Hua replaced Narain Karthikeyan but finished the session slowest of the 24 runners and over ten seconds off the pace.