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As it happened: Friday practice one
By Geoff Creighton, Emlyn Hughes and Charles Bradley
The live commentary has ended. No further updates will be posted.
Kovalainen14:45 Hello everyone and welcome to the penultimate round of the 2013 FIA Formula 1 world championship - the United States Grand Prix weekend from the Circuit of the Americas, near Austin, Texas.

This is the second event to the held at the 5.513km track and, while talk of the championship has all-but died down after Sebastian Vettel's vice-like grip on the campaign, there is still a lot to look forward to over the next few days.

At Lotus, Kimi Raikkonen produced what could be the most expensive sick note ever seen in our sport. Several drivers were in line to move into what is still a prime race seat, before it was announced yesterday that Heikki Kovalainen will make his much-awaited return to the category. It will be interesting to see how quickly he can get up to speed with the E21 that Romain Grosjean is now getting a lot out of.

Further down the grid, motivation could be a problem in the opposite direction. Pastor Maldonado and Sergio Perez have both announced in recent days that they will be leaving their respective teams at the end of the season, so their efforts will undoubtedly be under scrutiny this weekend.

Up front, the ever-present task of catching Vettel remains. The drivers have another chance to go at Red Bull, starting with Friday practice. As usual, we will start with the round of installation laps and aerodynamic tests, before the teams move into more general set-up work.

14:48 Here's how the standings look heading into the penultimate round:
World Championship standings, round 17:

Drivers:                      Constructors:
 1.  Vettel        347        1.  Red Bull-Renault          513
 2.  Alonso        217        2.  Mercedes                  334
 3.  Raikkonen     183        3.  Ferrari                   323
 4.  Hamilton      175        4.  Lotus-Renault             297
 5.  Webber        166        5.  McLaren-Mercedes           95
 6.  Rosberg       159        6.  Force India-Mercedes       77
 7.  Grosjean      114        7.  Sauber-Ferrari             45
 8.  Massa         106        8.  Toro Rosso-Ferrari         32
14:51 It is a foggy start at the COTA and we could be talking to you about weather for a while, given the lack of visibility around the track at the moment.

The good news is that the fog bank is expected to burn away by around 10 o'clock local time and we should be fine thereafter, with increasing sunshine and no threat of any rainfall across the three days.

There will be a light south-westerly breeze and air temperature will climb to 25 degrees Celsius later this afternoon.

Tyres14:54 Pirelli's medium and hard compounds make up the rubber allocation this weekend.

"it's a circuit that places several high-energy demands on the tyres," says the manufacturer's motorsport boss Paul Hembery. "So you need the most durable compounds in the range.

"There are some fast corners and many rapid elevation changes as well: in that respect it's a bit like Spa. When you have more energy going through the tyre, you have a bigger heat build-up - which is what increases wear and degradation."

14:55 Five minutes to the scheduled start of the session and still no confirmation if the session can begin in this heavy fog.

14:55 A ten minute delay has now been announced by race control.

14:56 As ever, the reason for this delay is that the medical helicopter is unable to fly.

14:56 Race control promises a further bulletin at 09:05 local time, five minutes after the session was due to start.

14:58 At Toro Rosso, the highly-regarded Daniil Kvyat will get his first official outing in a Formula 1 car for this session, as he gathers data in place of Jean-Eric Vergne.

14:58 Visibility shows little sign of improvement for the moment, so this delay could extend for quite a while.

15:03 At Mercedes, Lewis Hamilton looks in a good mood, as he shares a joke with some of the mechanics. Meantime, Mark Webber wanders outside to take a look at the latest weather conditions.

15:05 A further 10 minute delay has been confirmed by the FIA.

15:05 At Caterham, local boy Alexander Rossi will be gathering data for the team this morning, in place of van der Garde.

15:07 Conditions are slowly beginning to improve, as the sun starts to burn a hole through the fog bank. But make no mistake, this will be a lengthy process and we could easily be another 20-30 minutes before the drivers finally get out on track.

15:13 Pastor Maldonado is down there in the Williams garage, chatting away with one of the engineers. Rather it's a monologue, with the Venezuelan doing all the talking. He's done a lot of that over the past couple of days...

15:15 The inevitable delay extension is declared, with another 10 minutes - at least - to wait.

15:19 A pleasant chat down there between ex-team-mates, as Lewis Hamilton wanders down to Lotus to speak with Heikki Kovalainen.

15:20 At Red Bull, Vettel is in tool chest position with team boss Christian Horner and Helmut Marko beside him.

15:21 One driver change we didn't mention this morning is at Marussia. Rodolfo Gonzalez is at the wheel again and he will be gathering data, in place of Jules Bianchi.

15:23 Conditions are continuing to improve slowly, as the sun burns away the fog and you can see almost all of the way up the pit straight now.

15:26 Improving it may be, but another 10 minute delay is announced.

15:28 A one-hour practice session is now set to get underway at 9.40 local time.

15:30 That means the shortened practice will get underway in 10 minutes.

15:31 While half an hour of running has been lost to the fog, teams generally have quite a relaxed first practice plan due to tyre allocation.

15:33 An hour will still give outfits a good chance to make the most of the single set of hard tyres allocated per driver.

15:37 Drivers begin to prepare for the start of the delayed session, with teams busy thinking about the best way to use the hour of practice.

15:37 Hazy sunshine now burning through the fog and visibility is much improved than it was 20 minutes ago.

0 min: Practice is finally underway at Austin.

0 min: Kovalainen is the first man out in his Lotus.

0 min: Hulkenberg quickly joins him on circuit in the Sauber.

1 min: Kvyat heads out for the first time, followed by Toro Rosso team-mate Daniel Ricciardo, as their check over the machinery.

1 min: Grosjean, Massa, Alonso and Button are among those quickly taking to the circuit.

1 min: Vettel and Bottas join the racetrack for an installation run.

2 min: Rosberg and Maldonado head out, as the early runners bring their cars back into the pitlane after one lap.

3 min: Webber and Hamilton are on the circuit, as the sun is now blazing down over the circuit. Such a dramatic change in conditions in the last 20 minutes.

3 min: Most drivers heading back to the pits for a traditional set of installation checks after the first lap of the weekend in the cars.

4 min: Rossi heads out in his Caterham to take to the track on his home soil.

4 min: Practice start for Vettel after coming through the pitlane after one tour of the circuit. He is now into a second lap.

5 min: Ricciardo has completed a second lap of the track and comes into the pits at the end of his installation run.

5 min: Button is the first man to clock a time at 1m41.943s.

6 min: Button comes around again for an improved best of 1m40.468s.

7 min: Vettel continues round into a third lap of the track in the Red Bull.

8 min: Kovlalainen returns to the Lotus garage as the team announce that Raikkonen's back surgery yesterday was "totally successful"

8 min: In the garage, Hamilton complains: “The furniture outside is all in the way of my box, I thought I was going to hit it.”

9 min: Perez is an early second fastest, with Rossi currently third on the board.

10 min: While the McLaren pair and Rossi circulate, it is data download time in the pits for the others, following that raft of installation laps.

10 min: Button continues his early run with a new benchmark of 1m39.493s.

11 min: Perez improves his time and is now just under two tenths off his team-mate's current session topper.

12 min: Kvyat heads out there in the Toro Rosso, followed by team-mate Ricciardo.

13 min: Button reports: “There is a bit of understeer in the car, wouldn’t really want to go much more than a turn [of front wing].”

13 min: Perez is pushing at the moment and brakes a touch late for the first corner, locking up heavily into the uphill left-hander.

13 min: Rosberg is next out onto the circuit and suddenly we have 14 drivers out there.

13 min: New boy Kvyat is told: “Warm the brakes and tyres.”

14 min: Hulkenberg is up to third in the early times.

14 min: Hamilton and Sutil join the racetrack, leaving di Resta as the only man yet to leave the pits this morning.

14 min: The session has been stopped.

14 min: The reason for the red flag is unclear at the moment.

15 min: Race control announces "further problems with the medical helicopter"

16 min: The helicopter is not currently on site at the circuit, but it is bright and sunny overhead now.

17 min: There is some haze in the direction of downtown Austin, which could be a concern for any evacuation to the local hospital.

18 min: Marussia's Gonzalez reports from the garage: “Track is slippery, on the power and everything. Tyre temperature is crucial because it’s so slippery.”

20 min: The clock is continuing to count down under the red flag, with 40 minutes of this curtailed session remaining.

20 min: So, with nothing happening on track here is the situation. We are 20 minutes into a one-hour first practice session. Button leads the early group with a time of 1m39.493s.

16:01 His McLaren team-mate Perez is second, with Hulkenberg third, Rossi fourth and Pic the only other driver to have posted a time in fifth spot.

16:01 After his run, Ricciardo reports of his Toro Rosso's balance: “Both front and rear axles need time to get up to temperature, quite a lot of sliding.”

16:02 Several drivers were on the circuit for a first meaningful run since the installation lap, when the red flag was thrown.

16:02 The clock has now been stopped and reset to the moment of the red flag, with 45m53s remaining.

16:03 Caterham takes advantage of the delay to make a geometric change to the steering of Pic’s car.

16:04 Meanwhile, Kovalainen is giving his feedback to the Lotus mechanics and looking for some cockpit adjustments to get comfortable in the car.

16:05 Nico Rosberg remains in the cockpit of his Mercedes, as he waits for confirmation on when the session will resume.

16:10 This could be another lengthy delay as organisers scramble to get a helicopter available for emergency use.

16:11 Pic is told he will get seven or eight laps on his next run, when the session restarts.

16:17 At Red Bull, Mark Webber takes the opportunity to have a chat with the engineers and his father Alan, as they are introduced to one of the VIPs.

16:18 Finally a helicopter is spotted and is currently parking up outside the medical centre.

16:19 The clock has resumed, meaning the session will end at the top of the hour.

19 min: Some movement down in the garages as drivers begin to get ready once again. Felipe Massa has remained in his Ferrari all the while.

21 min: Still red flag conditions for the moment, with some confusion over whether that was the right helicopter sighted recently.

22 min: With a mandatory two-hour gap between practice sessions, the time is now running down to complete the hour.

22 min: Definitely not, as the two large empty helipad spaces remain unoccupied at the end of the pitlane.

24 min: Excitement builds as another chopper is spotted. Is this one of the medical variety?

25 min: One shiny blue and yellow helicopter now touches down, as a restart at 10:28 is announced.

27 min: Engines fire with just 20 seconds now to the restart.

28 min: We're finally back underway at Austin.

28 min: Di Resta is first out onto the circuit. He is yet to complete an installation run.

29 min: Ricciardo is asked if he is ready. He deadpans: “I’ve been ready for an hour and a half.”

29 min: Hamilton, Rosberg, Kvyat and Ricciardo all join the circuit.

29 min: Maldonado joins the racetrack in his Williams.

29 min: That delay has increased the urgency in this session, with many drivers out already to get some laps in.

29 min: Kvyat is told to ditch his constant-speed run and to head straight into his run plan.

30 min: Field flooding out now, with only the McLaren pair and Vettel in the garages.

30 min: Di Resta launches straight into a timed lap in the Force India.

31 min: All but the McLaren drivers on the circuit now, as teams look to make the most of the 29 minutes remaining.

32 min: Kvyat puts a time of 36m21.855s on the board thanks to that stoppage - a stunning start to his Formula 1 career - before coming up with a more respectable 1m46.755s.

32 min: Alonso joins the times in third fastest.

33 min: Webber is on the board in fourth for Red Bull, with Maldonado fifth, but only briefly as the times change again.

33 min: Hulkenberg takes fourth, with Massa fifth as the early pace from the McLaren pair holds the top of the order for now.

33 min: Di Resta completes a lap and he moves into sixth spot with 1m40.639s.

34 min: Perez complains: “I need more volume on the radio.”

34 min: Ricciardo then moves into fourth position in the Toro Rosso with 1m40.276s.

34 min: The two McLarens continue to lead the pack with Alonso third, Ricciardo fourth, Hulkenberg fifth and Bottas in sixth.

35 min: Hulkenberg ups his pace to third fastest, while Alonso sets the fastest time in the first sector.

35 min: Kvyat is informed: “You went forwards with the brake bias, we want you to go backwards, in the opposite direction. Four clicks.”

36 min: Vettel is the last to post a time on the board. He crosses the line and moves into 19th with 1m43.362s.

36 min: Massa briefly takes fourth fastest as long runs on the hard tyres continue.

37 min: Maldonado improves his time in the Williams and is up to fourth with 1m40.010s.

37 min: Hulkenberg reports: “Quite a bit of understeer, front-left tyre is suffering quite a lot of damage.”

37 min: Alonso tops the times in 1m38.767s.

37 min: Ricciardo takes that fourth spot away from the Venezuelan with a time of 1m39.933s, but they are suddenly tumbling down the order...

38 min: Webber jumps up to second spot, behind Alonso with a lap of 1m39.363s.

38 min: Bottas jumps up to second place behind new pacesetter Alonso, with a time of 1m38.901s.

40 min: Alonso is instructed to do a “slow lap, then a quick lap time, then the procedures.”

40 min: Button improves his earlier best, now third fastest in his McLaren.

40 min: Bottas finds an improvement of one-tenth of a second, with a new time of 1m38.802s. He remains in second spot.

40 min: Grosjean has some tyre pressure concerns, but is told that "it's nothing crazy."

41 min: Webber moves back up the order to fourth position with a time of 1m39.133s.

41 min: Alonso improves his leading time with a new best of 1m38.343s.

41 min: Massa is warned: “The pitstop is very, very slippy.”

43 min: Button reports: "The steering wheel is down to the left."

43 min: Grosjean has been for a little excursion over the popular run off on the outside of the tricky Turn 19.

43 min: Hamilton brings the Mercedes out for another run. He is 15th at the moment with a best time of 1m39.977s after 10 laps.

43 min: Ricciardo reports: “Change of direction is very lazy.”

44 min: Webber pits the Red Bull. He has completed nine laps of the track this morning.

44 min: Kovlainen is up to 10th fastest as he begins to get used to his Lotus after 12 laps in the car so far.

45 min: Alonso remains at the top of the pile, with 15 minutes of the opening session remaining. He is 0.045s clear of Bottas, with Button third.

45 min: Massa is fourth in the other Ferrari, ahead of Webber fifth, Hulkenberg sixth, Maldonado seventh and Grosjean in eighth spot.

46 min: Ricciardo leaves the pits for another run in the Toro Rosso. He is down in 14th on the timesheet and only two-tenths clear of Kvyat at this stage.

47 min: Gonzalez, meanwhile, is well off the pace at the rear of the field with a best some 7.3s away from the benchmark.

47 min: Rossi reports of his balance since a front wing change: “Progressively getting more understeer. Change of direction felt slower, less responsive.”

49 min: Hamilton moves himself up the order to eighth position, after posting 1m39.166s.

49 min: A number of drivers in the pits at the moment as teams ponder the data gathered so far before a late run to the flag.

50 min: Second placed Bottas is back out for another run with less than 10 minutes of the session remaining.

51 min: Webber and Maldonado also join the racetrack for another run of laps.

51 min: Pic reports: “Too much understeer. We can go one step stiffer at the rear.”

52 min: Gutierrez is up to fourth fastest in his Sauber with a personal best of 1m38.532s.

52 min: Meantime, Ricciardo came out, but was unable to improve on 15th. The gap between the Australian and Kvyat remains at just two-tenths.

52 min: Perez is told: “We can’t do any more timed laps because of the flatspots, so rubber the box.”

52 min: Ricciardo has completed a run through the pits and is back out onto the circuit.

53 min: Webber enquires: “Everything OK on the brakes, mate? Losing the rear at Turn 1.” He’s told it’s slow front-brake warm-up.

53 min: Sutil has run wide at Turn 19 but the German is able to continue and complete his latest effort. He is in 14th position.

54 min: Daniil Kvyat is back out for another run and we have 19 drivers on the circuit.

55 min: Quite a bit of running to the flag now, with teams keen to make up for the time lost to the helicopter delays earlier.

56 min: Gutierrez asks if his engineer wants him to do another run. “For me? Not really.”

56 min: Replays of Vettel and then Bottas locking up their tyres, as they work to gather data in the final minutes of the session. Both were able to continue.

56 min: Button is up to second fastest, just fractions off Alonso's best, with a 1m38.371s lap.

56 min: Hamilton is told: “Fuel corrected we think you’re around Alonso’s pace.”

57 min: Yellow flags and Gonzalez has stopped in his borrowed Marussia at Turn 13.

58 min: Smoke from the rear of the car now as Gonzalez complains of engine strife and steps out.

59 min: Nico Rosberg locks up both fronts heavily and misses the apex of Turn 1 by around three miles. He is able to continue on his run.

59 min: Yellows will remain out as the session finally draws to a close.

17:00 That's the flag on a disrupted first hour of practice at Austin.

17:01 Hamilton posts the fastest middle sector, but it doesn't help him and he remains in sixth spot, as the yellows remain out there for Gonzalez.

17:02 Fernando Alonso is fastest at the end of first practice at Austin, with a best time of 1m38.343s, 0.028s ahead of Jenson Button.

17:03 Bottas is an encouraging third for Williams, just 0.045s back, with Gutierrez fourth, Rosberg fifth and Hamilton in sixth spot.

17:03 Massa ends his morning in seventh place, with Webber eighth, Hulkenberg ninth and Maldonado rounds out the top 10.

17:04 Hulkenberg asks: “Where’s the top speed gain? None I could tell. Hell of a lot of understeer, overall.”

17:04 Further down the order, Daniil Kvyat deserves a mention for a good effort on his first outing. He completed 20 laps and ended up 17th.

17:05 Kvyat was just two-tenths of a second down on team-mate Daniel Ricciardo, while Vettel finished up his high fuel work in 18th spot.

17:06 Alex Rossi was another out there gathering data. At his home event, he completed 21 laps and ended up 19th, three seconds off the pace.

17:07 It's Alonso up front after the first hour, but we doubt he will stay there this afternoon. Join us later for second practice from Austin.

Session length: 60 minutes
Clear skies High Temp: 25°C / 77°F
Track: Dry
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Friday 15 Nov Start GMT
 Friday practice one 14:45
 Friday practice two 18:55
Saturday 16 Nov
 Saturday practice 14:55
 Qualifying 17:45
Sunday 17 Nov
 The US Grand Prix 18:30