Marc Marquez remained the man to beat in Saturday morning practice for the Indianapolis MotoGP race.
The championship leader burst to the front with a 1m38.844s lap in the closing minutes, becoming the first rider to break the 1m39s barrier this weekend.
Until works Honda rider Marquez showed his hand, satellite men Stefan Bradl and Cal Crutchlow had been battling for the top spot for much of the morning.
Bradl ended up second for LCR Honda, with Crutchlow's Tech 3 Yamaha preventing another all-Honda top three by beating Gresini's Alvaro Bautista to third.
Title contenders Dani Pedrosa and Jorge Lorenzo were only fifth and sixth, followed by Valentino Rossi.
Ben Spies is currently undergoing medical chats after a nasty crash. The American was making his comeback this weekend having been sidelined by injuries to his right shoulder for much of the year.
But a crash at Turn 4 resulted in a heavy landing on his other shoulder, leaving the American in clear pain.
His Pramac team-mate Andrea Iannone put in a very strong performance and was on course for Q2 before works Ducati rider Nicky Hayden squeezed him out by 0.017s with a last-minute lap.
Danilo Petrucci pipped Aleix Espargaro to top CRT honours in 12th.
Pos Driver Team/Bike Time Gap 1. Marc Marquez Honda 1m38.844s 2. Stefan Bradl LCR Honda 1m39.125s +0.281 3. Cal Crutchlow Tech 3 Yamaha 1m39.441s +0.597 4. Alvaro Bautista Gresini Honda 1m39.538s +0.694 5. Dani Pedrosa Honda 1m39.569s +0.725 6. Jorge Lorenzo Yamaha 1m39.597s +0.753 7. Valentino Rossi Yamaha 1m39.640s +0.796 8. Bradley Smith Tech 3 Yamaha 1m39.765s +0.921 9. Andrea Dovizioso Ducati 1m39.812s +0.968 10. Nicky Hayden Ducati 1m39.889s +1.045 11. Andrea Iannone Pramac Ducati 1m39.906s +1.062 12. Danilo Petrucci Ioda-Suter-BMW 1m40.879s +2.035 13. Aleix Espargaro Aspar Aprilia 1m40.895s +2.051 14. Ben Spies Pramac Ducati 1m41.451s +2.607 15. Yonny Hernandez PBM Aprilia 1m41.707s +2.863 16. Colin Edwards Forward FTR-Kawasaki 1m41.845s +3.001 17. Claudio Corti Forward FTR-Kawasaki 1m41.853s +3.009 18. Hiroshi Aoyama Avintia FTR-Kawasaki 1m42.041s +3.197 19. Hector Barbera Avintia FTR-Kawasaki 1m42.042s +3.198 20. Bryan Staring Gresini FTR-Honda 1m42.375s +3.531 21. Randy de Puniet Aspar Aprilia 1m42.583s +3.739 22. Michael Laverty PBM-Aprilia 1m42.647s +3.803 23. Lukas Pesek Ioda-Suter-BMW 1m42.789s +3.945 24. Karel Abraham Cardion Aprilia 1m43.325s +4.481 25. Blake Young Attack APR-Kawasaki 1m44.956s +6.112