Thick fog delayed the start of Friday morning's opening free practice session at the Circuit of the Americas ahead of Sunday's United States Grand Prix. On a mild morning with many fans in shirtsleeves, it was impossible to see more than 60 metres at the track, making it impossible to use medical helicopters. This meant that on-track action at the Lone Star state?s circuit was postponed twice by 10 minutes in the hope that the fog would lift ? and then allow one hour?s action instead of the normal 90 minutes. It was bad news not only for the fans, but also for drivers in need of track time including 19-year-old Russian Daniil Kvyat scheduled to have a run out with Toro Rosso, after swift promotion from GP3. He said of running in F1 in Texas and Brazil: ?These two outings are really important to learn these two tracks and get extra miles in an F1 car and try to get to know the team as quickly as possible.? Aware of the routine ruthlessness with which Red Bull treat their young drivers, dispensing with them if they do not come up to scratch, he conceded that ?Helmut Marko (the team's motorsport chief)just told me I have to deliver'." Similarly Finn Heikki Kovalainen, returning with Lotus as replacement for his Ferrari-bound compatriot Kimi Raikkonen, who is undergoing back surgery, was keen to start learning about team and car after his time with Caterham. ?Only time will tell how things go, but I expect myself to perform well,? said Kovalainen, who had one season with Lotus in 2007. ?I've been in Formula One long enough, even if I haven't driven much this year. For me, the main focus this weekend is not trying to show what I can do, but trying to deliver for the team. ?I'm here for the team more than myself. I haven't spoken to Lotus about next year at all. ?The only team that I've really spoken seriously to is Caterham [who released him as their reserve driver for these two races], and we're getting to a point where we're closer to starting to agree terms, so I think that's still the most likely option for me. ?You never know in this paddock, but I don't feel any extra pressure. I don't see these races as deciding what happens [next year]."