Friday at the Circuit of The Americas ended productively for both drivers despite a challenging start. The morning session began under cloudy skies with drizzle in the air, making track conditions difficult to read and data gathering tricky.

On his first run after the installation lap, the team detected a hydraulic issue on Fernando's car, and his session was aborted while the team investigated the issue and endeavoured to fix it. The team managed to get him back out on track 10 minutes before the end of the session, but weren't satisfied with the fix, and despite a total of four installation laps did not set a time.

The team opted to flip Fernando's test programme to Stoffel's car in an effort to gather as much data as possible, which meant a very busy but productive session for him. His run plan consisted of aero correlation, set-up changes with new components and tyre tests, which were completed successfully and he finished the first session in fifth place after 26 laps.

Both drivers had a more productive second session, completing longer runs and making various set-up changes during a number of practice pit stops. Fernando completed 28 laps, Stoffel 31, and they finished seventh and 15th respectively on the timesheets.

Fernando Alonso: "We lost the first session this morning because of an hydraulic issue, which was quite painful because we had several items to test, including for next year. We tried to catch up in the second session but it was difficult, so I think we'll try them again in Mexico.

"I believe there's still quite a bit to get out of the car - still some tenths to find, which I think probably everyone will find.

"We know Verstappen and Hulkenberg have penalties, so if we manage to get into Q3 tomorrow, we'll be able to start from an even better position. But if we don't make it into Q3, and we can start eighth or ninth on new tyres, it could be very good too.

"It's nice to drive on this track with this year's cars. It's much more fun, especially through the fast corners in the first sector. There are many more bumps than last year, so we're holding tight on the steering wheel and with the seatbelt tightly fastened. But it's fun!"

Stoffel Vandoorne: "Today was a reasonable Friday overall. This morning we faced tricky conditions to start with, but in the end it dried up and we had a really busy first practice session trying out some new aero parts. I feel that I put in a good performance, especially considering it was my first time driving on this circuit.

"FP2 was a bit more difficult for me. We struggled during the session with some traffic and I wasn't 100 per cent happy with the car balance, but the long-run pace looked reasonable - I was a bit happier with our long-run pace than qualifying set-up.

"All in all, tomorrow we have a lot of margin to improve, but we know what we have to do and hopefully we should be lot closer."

Eric Boullier: "After a tricky start to the morning thanks to the mixed conditions, we've managed to make good headway with our run programme despite a compromised first session for Fernando, leading us to swap the test plan between our two cars. Both the team and drivers adapted very well and pushed hard to complete a lot of useful running in both sessions.

"Much of our running today was spent evaluating various components and conducting run plans to set us up for race day. This is a track that suits our car better than most, so it's important that we prepare ourselves as best we can to maximise every opportunity on Sunday. Stoffel's pace in the first session was encouraging and both drivers collected a good amount of data from their longer runs this afternoon, so we look to be in good shape going into Saturday.

"We still have a lot of work to do before both drivers are happy with the set-up of the car, but, providing we can maintain good reliability, we hope we can have another productive day tomorrow where we can put ourselves in the best possible position in qualifying. Although Stoffel has a five-place grid penalty, Q3 has to be our aim for both cars and we'll see what we can do from there."

Yusuke Hasegawa: "The first day of the United States Grand Prix began with unstable, damp weather making for tricky practice conditions. Nevertheless, Stoffel was able to run though his programme as scheduled. Fernando lost some time in FP1 after the team detected a hydraulic issue, but recovered enough track time in FP2 to gather sufficient data.

"There is definitely more room to improve in terms of the set-up in FP3 for both cars, and I still think we are capable of reaching Q3 in tomorrow's qualifying.

"This weekend we have introduced a new ICE in Stoffel's car, and as a result he will incur a five-place grid penalty for the race on Sunday. Despite this we have a positive feeling about our PU after today's session and we think our package will be quite competitive here."

Check out our Friday gallery from Austin, here.