MONTMELO, Spain -- Max Verstappen topped the opening practice session for this weekend's Spanish Grand Prix as a number of teams tested upgrades for the first time.
There was a familiar look to the timesheets as Verstappen led Red Bull teammate Sergio Perez by 0.768s, who in turn was 0.044s ahead of Monaco podium finisher Esteban Ocon in third.
Ocon's Alpine was among the few cars with no upgrades this weekend, while Ferrari tested a new sidepod and bodywork design for the first time, Aston Martin tested a new nose, front wing and rear wing and Mercedes continued to add to its major upgrade package introduced in Monaco.
Red Bull had two relatively small tweaks to its floor edge and diffuser, the latter of which it said was inspired by the designs of competitors.
Gaining an understanding of the new parts might explain why Ferrari finished the session in eighth and ninth, Aston Martin in sixth and 15th and Mercedes in 10th and 12th. Ferrari chose to run its new parts on Carlos Sainz's car while keeping Charles Leclerc's car in the old specification to offer a comparison.
In the absence of Red Bull's closest competitors at the top of the timesheets, Nyck de Vries was fourth fastest for AlphaTauri, with a car featuring a new rear wing, and Pierre Gasly was fifth fastest in the second Alpine.
As part of a confirmation test for tyre supplier Pirelli, each driver has two extra sets of a new hard compound to use on Friday, which will be introduced from the British Grand Prix onwards to cope with the increasing speed of the current generation of cars.
Second practice gets underway later on Friday, but with rain in the air it could prove less useful for team's understanding of their cars.