Tricky conditions affected a number of drivers in practice as Red Bull's Max Verstappen was the fastest around Qatar’s Losail International Circuit.
Wind, sand, dust and a slowly setting sun made the track particularly difficult to navigate in the weekend's only practice session, with qualifying taking place later on Friday ahead of Saturday’s sprint.
Max Verstappen knows that he only requires three points to secure his third world title in Qatar, and he'll have no doubt been pleased to top the timings in practice.
In what seemed like a challenging session for Red Bull, the Dutchman encountered several off-track moments, at least as many as those experienced by other drivers.
For much of the session, he found himself in a lower position before making his final run, as did Perez, who leapt from last into fifth place with a soft tyre run towards the end of the session.
Alonso impresses
Fernando Alonso had led the session leading into the last 30 minutes, and his subsequent time of 1:27.919 secured him fourth place overall.
This achievement was notable considering the evident grip advantage provided by soft tyres, with Alonso staying out and setting his time on the slower mediums.
Drivers struggle with Qatari conditions
Practice was largely dominated by talk of difficult driving conditions, with Leclerc, Verstappen, Lewis Hamilton and Alex Albon among those who struggled to keep their cars on the track.
Norris' front wing sliced through a polystyrene board early in the otherwise quite uneventful session.
Qatar Grand Prix FP1 practice results - Friday October 6