US GP: Fernando Alonso leads bizarre first practice for Ferrari

The Spanish Ferrari driver posted a best time of 1m38.343s to finish ahead of McLaren's Jenson Button and Valtteri Bottas in the Williams.

Esteban Gutierrez was fourth fastest for Sauber ahead of Mercedes' Nico Rosberg.

Formula 1 world champion Sebastian Vettel had a low-key start to the weekend, finishing down in 18th position.

The fog caused a delay of 40 minutes because the medical helicopter could not take off, meaning the session was shortened to just an hour rather than the scheduled 90 minutes.

Button was the first man to set a time and also the fastest driver for several minutes before the action came to a halt when practice was red-flagged because of "further problems with the medical helicopter", which, as was later revealed, was not on site.

The countdown clock was restarted with 45 minutes to go, but the action could not resume as the track was still closed as teams waited for the medical helicopter to land at the circuit.

Once the helicopter appeared on track, the action finally resumed with some 32 minutes on the clock.

Alonso put his Ferrari on top quickly after the action continued, the Spaniard setting a laptime of 1m38.343s that would remain unbeaten.

Kimi Raikkonen's stand-in Heikki Kovalainen, one of the men who will have lamented the lack of running, finished in 13th position in the second Lotus.

Toro Rosso's Daniil Kvyat completed his first practice run for the team he will race for next year, the Russian posting the 17th quickest time, winding up right behind team-mate Daniel Ricciardo.

Local hero Alexander Rossi, in his first F1 outing in front of his home crowd, finished 19th for Caterham.

Marussia's third driver Rodolfo Gonzalez caused the only significant on-track incident when he stopped with an apparent problem with two minutes remaining.

Pos Driver                Team                    Time       Gap      Laps
 1. Fernando Alonso       Ferrari                 1m38.343s            16
 2. Jenson Button         McLaren-Mercedes        1m38.371s  +0.028s  25
 3. Valtteri Bottas       Williams-Renault        1m38.388s  +0.045s  17
 4. Esteban Gutierrez     Sauber-Ferrari          1m38.532s  +0.189s  18
 5. Nico Rosberg          Mercedes                1m38.657s  +0.314s  21
 6. Lewis Hamilton        Mercedes                1m38.979s  +0.636s  21
 7. Felipe Massa          Ferrari                 1m39.005s  +0.662s  17
 8. Mark Webber           Red Bull-Renault        1m39.083s  +0.740s  17
 9. Nico Hulkenberg       Sauber-Ferrari          1m39.158s  +0.815s  17
10. Pastor Maldonado      Williams-Renault        1m39.200s  +0.857s  15
11. Romain Grosjean       Lotus-Renault           1m39.238s  +0.895s  13
12. Sergio Perez          McLaren-Mercedes        1m39.256s  +0.913s  17
13. Heikki Kovalainen     Lotus-Renault           1m39.487s  +1.144s  18
14. Adrian Sutil          Force India-Mercedes    1m39.699s  +1.356s  15
15. Paul di Resta         Force India-Mercedes    1m39.836s  +1.493s  15
16. Daniel Ricciardo      Toro Rosso-Ferrari      1m39.863s  +1.520s  19
17. Daniil Kvyat          Toro Rosso-Ferrari      1m40.065s  +1.722s  20
18. Sebastian Vettel      Red Bull-Renault        1m40.662s  +2.319s  21
19. Alexander Rossi       Caterham-Renault        1m41.399s  +3.056s  21
20. Max Chilton           Marussia-Cosworth       1m41.605s  +3.262s  19
21. Charles Pic           Caterham-Renault        1m42.054s  +3.711s  19
22. Rodolfo Gonzalez      Marussia-Cosworth       1m43.716s  +5.373s  17