George Russell set the fastest time during a disrupted session which saw four red flags.
His time of 1min 19.233sec is the fastest so far of the test, but he did it in amongst a bevy of stoppages.
Fernando Alonso had put in the quickest laps early on, but his session quite literally went up in smoke when his car broke down after 14 laps. The fire damage that resulted was so severe that Alpine confirmed that its running is over prematurely for this week’s test.
Several cars got out for the early running, with Max Verstappen putting in the second fastest lap of 1min 19.756sec. He also set the most laps at 69.
In third was Sebastian Vettel. The German had shown reasonable (relative) pace, but his run then came to a halt when his car stopped towards the end of this morning’s session – the Aston Martin was 0.15sec off Verstappen.
Charles Leclerc and Ferrari had a more low-key morning than has been normal over last two days, but 44 laps and 1min 19.824sec represented a solid morning’s work.
Nicholas Latifi was next along in sixth, scoring a 1min 20.699sec but only managing five laps.
Lando Norris completed his running in Barcelona with seventh quickest time of the morning and a decent chunk of laps – 52 brought his week’s running to 155 in total.
Alonso’s early turn-in of 1min 21.242sec left him seventh before his mechanical failure, but Guanyu Zhou bested him on the red flag-front, bringing out two. One for an off in the last sector, then stopping on the pit straight as soon as the green flag fell again.
Pierre Gasly, whose 1min 22.469sec eventually put him ninth, also had an off which brought the session to a stop, damaging his front wing in the crash.
Williams’ Alex Albon was two tenths off the Frenchman, with Nikita Mazepin coming in slowest.