Robert Kubica has ended the morning session of testing from Barcelona on top of the timesheets, clocking a 1:16.942 for Alfa Romeo.
The Polish driver's time was set on the C5 compound, the softest Pirelli tyre available to the teams during testing.
Behind Kubica came Pierre Gasly, as both AlphaTauri and Red Bull had less productive morning compared to the test sessions that they went through last week.
Vettel had a spin at Turn 7 which caused a red flag due to gravel being deposited on the circuit. However, he avoided the barrier and returned the garage.
Romain Grosjean rounded out the top ten of Haas, with the Frenchman being the only driver not handing over to his teammate for the afternoon session.
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