15:48 - Meanwhile if you want to catch up on today's action then don't miss out report on the second free practice session: Rosberg leads Ricciardo and Hamilton in FP2
15:42 - We'll be back with as-it-happens coverage of FP3 tomorrow at 10am local time (4pm BST) - please do join us for that, and for qualifying later in the day.
15:40 - That about wraps it up for our live coverage of Friday's action at the Circuit of the Americas. Don't forget, the F1i website will keep you updated with all the news this evening and overnight.
15:36 - Raikkonen will likely be a bit disappointed with only the tenth fastest time in FP2. It was also a bit of a slump for Williams with Bottas finishing in 14th and Massa down in 16th. And definitely not the sort of home race that Haas were looking for, as Grosjean ends up 18th and Gutierrez in 20th.
15:35 - Promising runs for Force India with Hulkenberg and Perez in sixth and seventh; and also for McLaren who take eighth and ninth for Button and Alonso respectively.
15:34 - So honours for Friday are split between the two Mercedes drivers - Hamilton was fastest in the morning but Rosberg took control in the afternoon. Red Bull signal they might be a threat this weekend with Ricciardo second, while Vettel flies the flag for Ferrari ahead of Verstappen.
15:32 - Here's the final times and positions for FP2: 1 Ros (1:37.358s), 2 Ric (+0.194s), 3 Ham (+0.291s), 4 Vet (+0.820s), 5 Ves (+0.900s), 6 Hul (+1.150s), 7 Per (+1.210s), 8 But (+1.355s), 9 Alo (+1.443s), 10 Rai (+1.507s), 11 Sai (+1.613s), 12 Mag (+1.801s), 13 Nas (+1.831s), 14 Bot (+1.839s), 15 Kvy (+1.844s), 16 Mas (+1.923s), 17 Pal (+2.097s), 18 Gro (+2.196s), 19 Oco (+2.728s), 20 Gut (+2.756s), 21 Eri (+2.861s), 22 Weh (+3.773s).
15:31 - Just before the chequered flag there was a brief yellow as Carlos Sainz flew off the track in turn 18. His tyres are shredded so he had to head for the pits rather than complete his session and try some practice starts.
15:30 - Your 90 minutes are up! That's the end of Friday's free practice.
15:29 - Looks like Red Bull and Ferrari have good long distance race pace - perhaps even an equal to Mercedes.
15:25 - Five minutes remaining. We're not expecting the timing screens to change before the chequered flag.
15:24 - It really is quite crowned out there. It feels more like the early laps of a race than a practice session, with many cars running close together.
15:22 - More reports of debris in turns 5 and 6. The pieces of bodywork seem to have dropped off Gutierrez's Haas.
15:20 - Wehrlein is now back in action, so all 22 cars are currently out on track. That's causing quite a lot of congestion, as Red Bull confirm to Verstappen who is struggling to find some clear track.
15:18 - "Nothing left on these tyres," reports Vettel after 20 laps on his softs.
15:17 - Now Raikkonen has tyre issues: "I have no front end, because the left front has gone," he says before pitting.
15:14 - Verstappen joins the chorus of drivers complaining about their tyres, just four laps into a stint on the soft compound. Rosberg's also struggling for grip and has had a minor off at the penultimate corner. He reports "strange oversteer."
15:13 - Ericsson also reports that his supersoft tyres are falling part after 12 laps. "They're falling apart completely, both front and rear," he tells Sauber.
15:12 - Hamilton reports a problem with vibration on the current set of medium tyres on the Mercedes, seven laps into this stint.
15:11 - Jolyon Palmer spins off onto the grass at turn 8/9. He slowly recovers to the track under local yellows and sounds perfectly calm on the team radio.
15:10 - Bottas is struggling for grip and locking up as he finds the end of life of his current set of tyres.
15:07 - Hulkenberg comes out to play, leaving Wehrlein the sole man still on pit lane. Not sure if the Manor has a problem or whether this is all part of the plan.
15:06 - Hulkenberg continues to sit out this part of the session. Also in the garage at the moment is Wehrlein.
15:03 - A replay appears to show a small piece of bodywork fall off one of the Haas cars and nearly hit Vettel's Ferrari.
15:01 - In fact just four cars stay in the pit lane at this point: Hulkenberg, Raikkonen, Grosjean and Ocon.
15:00 - Vettel and Verstappen are quick to go back out, with most of the field in quick pursuit behind them.
14:59 - A rapid return to green flag conditions. The clock continued to count down during the red flag so there's just over half an hour remaining in FP2.
14:57 - Still, safety first. The debris was at a point of the circuit where the drivers were unsighted by a small crest so they could easily have run into it. A marshall collects the largest bit of broken bodywork from the track.
14:56 - The debris is on the racing line in the fast turn 3/4/5 Esses. The red flag stoppage is going to disrupt everyone's distance runs. It seems a rather dramatic step simply to clear up some debris.
14:55 - Red flag, probably for debris?
14:53 - All but four cars are back out on track at the moment. In the garage are Button, Grosjean, Gutierrez and Ericsson.
14:50 - After all that quasi-qualifying action it looks like things have settled down into longer distance work. Grosjean was the last driver to try out the supersofts and improved to 18th with a time of 1:39.554s.
14:47 - Here's everyone's fastest lap times at this point of the proceedings: 1 N.Rosberg (1:37.358s), 2 D.Ricciardo (1:37.552s), 3 L.Hamilton (1:37.649s), 4 S.Vettel (1:38.178s), 5 M.Verstappen (1:38.258s), 6 N.Hulkenberg (1:38.508s), 7 S.Perez (1:38.568s), 8 J.Button (1:38.713s), 9 F.Alonso (1:38.801s), 10 K.Raikkonen (1:38.865s), 11 C.Sainz (1:38.971s), 12 K.Magnussen (1:39.159s), 13 F.Nasr (1:39.189s), 14 V.Bottas (1:39.197s), 15 D.Kvyat (1:39.202s), 16 F.Massa (1:39.281s), 17 J.Palmer (1:39.455s), 18 E.Ocon (1:40.086s), 19 E.Gutierrez (1:40.114s), 20 M.Ericsson (1:40.219s), 21 R.Grosjean (1:40.848s), 22 P.Wehrlein (1:41.131s)
14:45 - Rosberg and Ricciardo at the top of the times are both back out on track once again as we reach the halfway point of the 90 minute session.
14:43 - The McLaren prediction wasn't far off: Alonso produces a 1:38.801s to go eighth; Button then demotes him to ninth as he produces a lap of 1:38.713s.
14:42 - Now the McLarens move to the supersofts. They're well down the running order at present, but the team radio predicts a two second improvement on this compound compared to their previous runs.
14:41 - Perez is up to seventh now, six hundredths off his team mate Hulkenberg in sixth.
14:40 - Drivers are returning to pit lane for new tyres and consultations with their race engineers. Currently still out on track: Perez, Magnussen, Nasr, Palmer, Button, Alonso, Ericsson and Wehrlein.
14:35 - The other teams are also on qualifying simulations with the supersofts: Ocon improves to 11th with his run clocking in at 1:40.086s which is immediately beaten by Palmer, while Carlos Sainz then leaps up to eighth just ahead of Bottas and Kvyat.
14:34 - Things are changing every minute. Here's the latest standings: 1 Ros (1:37.358s), 2 Ric (+0.194s), 3 Ham (+0.291s), 4 Vet (+0.820s), 5 Ves (+0.900s), 6 Hul (+1.150s), 7 Rai (+1.507s), 8 Bot (+1.839s), 9 Kvy (+1.844s), 10 Mas (+1.923s), 11 Gut (+2.756s), 12 But (+3.215s), 13 Per (+3.250s), 14 Mag (+3.428s), 15 Gro (+3.490s), 16 Alo (+3.548s), 17 Sai (+3.616s), 18 Eri (+3.676s), 19 Oco (+3.791s), 20 Nas (+3.945s), 21 Pal (+4.783s), 22 Weh (+6.333s)
14:33 - Hamilton stays with them, posting a new lap of 1:37.649s which puts him up into third place. He's 0.291s behind Rosberg at this point.
14:32 - Rosberg's supersoft time extends his lead at the top: his lap was 1:37.358s. Ricciardo goes second just a couple of tenths slower.
14:31 - Verstappen's lap faded in the middle sector. His team mate Ricciardo is also on the supersofts and has gone purple in the first sector too.
14:30 - Verstappen switches to supersofts and sets a purple first sector. Rosberg has also made a move onto the supersofts.
14:28 - Hulkenberg also tries out the supersofts, and goes from 13th to fourth. His time was 1:38.508s.
14:25 - Vettel didn't initially look to be having much more luck than Raikkonen, but he puts in a great final sector despite himself running wide in turn 19, and leaps up to second place with 1:38.178s.
14:23 - Raikkonen is the first to try out the supersoft tyres this afternoon, but he's caught out by the tail wind into the penultimate corner during his flying lap and the time isn't as good as hoped for.
14:21 - All 22 drivers have now been out and set a time. Here's the current standings: 1 Ros (1:38.082s), 2 Ham (+0.312s), 3 Ric (+0.447s), 4 Ves (+0.459s), 5 Vet (+0.810s), 6 Rai (+0.848s), 7 Kvy (+2.178s), 8 Mas (+2.225s), 9 But (+2.491s), 10 Per (+2.526s), 11 Mag (+2.704s), 12 Gro (+2.766s), 13 Hul (+2.817s), 14 Alo (+2.824s), 15 Bot (+2.860s), 16 Sai (+2.892s), 17 Eri (+2.952s), 18 Oco (+3.067s), 19 Nas (+3.751s), 20 Gut (+3.993s), 21 Pal (+4.059s), 22 Weh (+5.609s)
14:17 - Ocon's back underway and the track is back to green.
14:15 - Ocon's lost the rear end going into turn 18 and spun off into the gravel in the final sector. He's trying to extricate himself under local yellows.
14:15 - Only three drivers have yet to post a time. Jenson Button is one of them and he's currently out on track; the two Saubers are yet to make a move, however.
14:14 - Red Bull is also out now and quickly slot into third and fourth with Verstappen just pipping Ricciardo.
14:13 - Hamilton's also in action but had a messy first lap. His second is better but only good enough for second behind Rosberg - 1:38.394s. However, he's on mediums while Rosberg is on the soft compound tyres.
14:12 - And Rosberg is also out and quickly down to work, topping the times with a lap of 1:38.082s.
14:11 - Correction, Massa is out for Williams and he's just popped into fourth place ahead of Perez with a lap of 1:40.307s.
14:09 - A flurry of early flying laps as more cars come out: Kvyat is third fastest, and Perez has just put in a lap good enough for fourth. No sign of Mercedes, Williams or Red Bull coming out so far.
14:06 - Now the Ferraris take over at the top - Vettel posts a time of 1:38.892s, just a few hundredths faster than Raikkonen. Alonso slots in between the two Haas cars.
14:04 - Grosjean goes top with 1:40.848s while Gutierrez is some way back on 1:42.246s and Wehrlein - who sat out FP1 - is third with 1:45.796s
14:02 - Grosjean and Alonso are also quick on the move.
14:01 - Wehrlein and Gutierrez are the first two drivers to take the to the track this afternoon. Both are on medium tyres.
14:00 - And we're underway for the 90-minute second free practice session!
13:58 - Just a couple of minutes to go now until we get FP2 underway.
13:56 - It's still bright and sunny in Austin, with temperatures now up to 21C (air) and 37C (track) which should help the teams get up to speed.
13:54 - Jenson Button seemed to suffer a power unit problem on his McLaren which ended his session prematurely, and Marcus Ericsson was stuck in low gear and had to limp back to the pits in his Sauber. There was also a problem for Sebastian Vettel who had to coast back to pit lane holding on to his right hand wing mirror which had been shaken loose when the Ferrari ran over the kerbs.
13:52 - Hopefully the teams that experienced glitches this morning will have rectified them over the lunch break. Both Haas cars stalled in the pit lane toward the end of FP1 and had to be wheeled back to their garage - not the sort of thing you want at the team's first-ever home Grand Prix!
13:50 - A reminder that the tyre compounds on offer from Pirelli here are medium, soft and supersoft.
13:48 - The best time of FP1 was 1:37.428s. The track started off rather dusty, and it was quite breezy and cool despite brilliant blue skies - a welcome change on the wet and stormy conditions we endured here 12 months ago.
13:47 - You can read our report of everything that happened this morning: Hamilton tops FP1 as Mercedes dominates in Austin.
13:46 - However it's worth pointing out that Hamilton and Rosberg were both on softs while Verstappen was sticking to the mediums for most of FP1, so that may not be a true picture.
13:45 - Lewis Hamilton was firmly in charge of this morning's 90 minute FP1, and he and Mercedes team mate Nico Rosberg were well out in front of third-place man Max Verstappen.
13:44 - Welcome back to F1i's live coverage of free practice for the United States Grand Prix at the Circuit of the Americas in Austin, Texas.