Dani Pedrosa set a blistering pace in the opening practice session for the Czech Moto GP at Brno on Friday morning.
The Spaniard, refreshed from the mini-summer break having suffered a sequence of injury issues, moved to the top of the times halfway through the 45-minute session.
The Honda rider then emphasised his pace with a sub-lap record 1m56.328s lap on his penultimate lap.
Championship leader Casey Stoner was second quickest - 0.966s behind his team-mate.
Marco Simoncelli was third quickest on the Gresini-run factory Honda, having set the pace early in the session. But his programme was not without drama as he lost the front on the left-hander before the pits and fell. Neither rider nor bike was particularly damaged in the crash.
World champion Jorge Lorenzo, sporting a Top Gun 'Maverick' crash helmet, was fourth fastest on the Yamaha, ahead of Andrea Dovizioso on the final of the factory Hondas
Ben Spies was sixth fastest on the second Yamaha, ahead of an impressive Jon Hopkins on the wildcard Suzuki. The American, on his second outing for the factory squad this season just outpaced team regular Alvaro Bautista, though both were two seconds off Pedrosa's pace.
Cal Crutchlow, on a circuit he knows, was ninth fastest on the Tech 3 Yamaha, just ahead of team-mate Colin Edwards.
Factory Ducati riders Valentino Rossi and Nicky Hayden were 11th and 14th.
Pos Rider Team/Bike Time Gap 1. Dani Pedrosa Honda 1m56.328s 2. Casey Stoner Honda 1m57.294s + 0.966s 3. Marco Simoncelli Gresini Honda 1m57.408s + 1.080s 4. Jorge Lorenzo Yamaha 1m57.587s + 1.259s 5. Andrea Dovizioso Honda 1m57.776s + 1.448s 6. Ben Spies Yamaha 1m57.903s + 1.575s 7. Jon Hopkins Suzuki 1m58.321s + 1.993s 8. Alvaro Bautista Suzuki 1m58.345s + 2.017s 9. Cal Crutchlow Tech 3 Yamaha 1m58.390s + 2.062s 10. Colin Edwards Tech 3 Yamaha 1m58.497s + 2.169s 11. Valentino Rossi Ducati 1m58.819s + 2.491s 12. Randy de Puniet Pramac Ducati 1m58.927s + 2.599s 13. Hector Barbera Aspar Ducati 1m58.973s + 2.645s 14. Nicky Hayden Ducati 1m58.975s + 2.647s 15. Hiroshi Aoyama Gresini Honda 1m59.289s + 2.961s 16. Karel Abraham Cardion Ducati 1m59.334s + 3.006s 17. Loris Capirossi Pramac Ducati 1m59.706s + 3.378s 18. Toni Elias LCR Honda 2m00.201s + 3.973s