Seven of the 11 teams participated on Monday: Red Bull, Mercedes, Racing Bulls, Haas, Alpine and the new teams Audi and Cadillac.
McLaren said last week that they would not take their car to the track until after the first day as a result of trying to maximize design time. Ferrari, after an initial test at its factory last week, also announced it would not race on Monday.
Aston Martin has said its new car will not be ready until Thursday, and Williams will miss the test entirely due to delays in its design and production schedule.
No times were issued and all teams had at least some technical problems when getting to know their new cars.
Rival teams were impressed by the amount of mileage both Red Bull teams achieved considering it was the first full day of running with their new in-house engine, which has been developed in conjunction with new partner Ford.
Before testing began, McLaren and Red Bull revealed images of their 2026 cars for the first time.
McLaren, which won the drivers’ and constructors’ championship last year for the first time since 1998, showed off the car in the unique test colors it will use this week.
Red Bull showed off studio photographs of its car, carefully chosen to disguise key design features.
Russell added: “We’re happy with our day but I’ve also been impressed by a number of other teams.
“The Red Bull power unit has completed many laps which, given that it is the first engine they have built, clearly means they have done a good job.
“Haas also achieved a similar amount of run to us, so the Ferrari power unit has also accumulated a lot of mileage. It’s not exactly what it was in 2014! The sport has evolved a lot since then and the level, in all aspects, is very high now.”
Audi has taken over the Sauber team for the German car company’s first entry into F1. They suffered a reliability problem that prevented Bortoleto from driving in the afternoon.
Team principal Jonathan Wheatley said: “We had a technical issue, we spotted it and decided to shut the car down. We’ve done a lot of testing this year and we wanted to really understand the issues, see what the weather conditions are and decide if we’ll race tomorrow.”
Rain is forecast for the second day of testing on Tuesday, during which teams will be able to race on up to three of the available days.
Bortoleto said: “The cars are very different. I feel like they’re going to be slower, but it’s great to have the power unit being 50% electric: you come out of the corner and you have so much speed on display and you can see how strong the engine is.”
“You have to adapt, but it’s still a racing car.”
Racing Bulls’ Lawson said: “[The car is] It’s very different from driving and I still haven’t fully understood it. We will continue learning. It seems like there’s a lot more we can do as drivers to make a difference, potentially, but at the moment it’s very early days, it’s very difficult to know where we are at the moment just trying to optimize the car.
“[The power unit] it feels good. But it’s very difficult to say: the main thing at the moment is reliability.
“We’ve done a fair amount of laps today and the only issues we had today were safety precautions, not real issues. But it’s hard to know where we are compared to everyone else.”
