Marc Marquez topped a shortened Sunday morning warm-up session ahead of the Aragon Grand Prix.
Morning fog that suspended track action for an hour meant that MotoGP's warm-up didn't commence until 10:55, and was cut by five minutes to 15.
Marquez, who qualified fifth on Saturday after crashing late on in Q2, was the first man to dip below the 1m50s barrier in warm-up with a 1m49.977s, which he lowered to a 1m48.976s next time around.
That time would have been enough to top the session, but the Repsol Honda rider was able to shave off another tenth and end the session with a best effort 1m48.832s.
His nearest challenger was Aprilia's Aleix Espargaro, whose 1m49.206s lap vaulted him ahead of Marc VDS Honda rider Jack Miller in the closing stages.
Miller held on to third, 0.658s slower than Marquez but fractionally up on Yamaha poleman Maverick Vinales in fourth place.
Cal Crutchlow made it three Honda riders in the top five in fifth ahead of KTM's Pol Espargaro, Avintia Ducati man Hector Barbera and Tech 3 Yamaha's Johann Zarco.
Valentino Rossi, who took a front row starting slot 23 days on from breaking his right leg on Saturday, was ninth-fastest in warm-up, 0.835s off the pace, while the Pramac Ducati of Scott Redding completed the top 10.
The session was a low-key one for works Ducati riders Andrea Dovizioso and Jorge Lorenzo, who wound up 14th and 16th respectively, while the Pramac-run GP17 of Danilo Petrucci was down in 17th.