A rain-affected day in Austin meant only limited running took place during either free practice session.
Lando took the wheel of Stoffel's car in the morning, but he and Fernando managed only nine laps each during the 90-minute session as the team opted for exploratory laps on both full Wets and Intermediate tyres to test the conditions. Lando finished just behind Fernando in 12th and 11th places respectively.
By the afternoon the rain was falling much heavier, so much so that Fernando only completed three laps at the tail-end of the session as the downpour subsided a little and a drier line started to emerge. Stoffel, who was yet to do any running at all, braved the conditions and managed a total of 10 laps - an exploratory two on full Wets, and then eight more on Intermediate tyres at the end of the session. The conditions meant the timesheets were fairly unrepresentative, with Fernando in fourth and Stoffel in eighth, and more rain forecast for tomorrow.
Fernando Alonso: "It was an odd day, with very wet track conditions and not much running. "It always feels good here, though, the high-speed section especially is quite impressive with these cars.
"Hopefully tomorrow we'll put in some more laps. We're always missing a couple of sets of tyres on Friday and it's a pity, especially for the people who come to watch us from the grandstands."
Stoffel Vandoorne: "My Friday wasn't very busy! I missed out on FP1 as Lando was in my car, and then in FP2 because of the bad weather conditions we only managed a couple of laps. But for me it was still good to get back to grips with everything after the Formula E test. Hopefully tomorrow I can get a few more laps in.
"This should be one of our better circuits. We've got a few new bits on the car, but with the weather conditions it's a bit difficult to prove them out.
"When it's tricky then generally that offers a few more opportunities for us, so we'll see how it goes tomorrow."
Lando Norris: "Today was good. It's my first time here, and second time ever in America. It's a cool track, really enjoyable. I think it'll be very different in the dry. It's very bumpy and you don't feel the bumps quite as much in the wet as you're on different lines.
"It was tricky because it was quite slippery, so I think there were a lot of people making mistakes here and there. It wasn't easy but everything I did felt pretty good.
"I know in myself I have a lot more time to improve and there are things for me to work on. I feel more comfortable, especially in the rain, as it's only my second time driving in the wet.
"It's difficult to adjust to all these different things - a new track, new conditions and trying new things in changing conditions. But it was a good session.
"When I'm not driving I'm now becoming a professional Barista, making coffee and tea for all the guys to pass a bit of time!"
Gil de Ferran, Sporting Director: "There's not much to report from today. We had the opportunity to test some items in the background that were on the list. The car seemed to be behaving quite well in these wet conditions.
"Obviously if these conditions persist tomorrow, we will be going into qualifying with very little dry running and preparation, which should make qualifying in many ways quite unpredictable.
"Currently the forecast is for a much drier Sunday, hence we'll have a lot of interesting decisions to make tomorrow."