Casey Stoner edged out works Honda team-mate Dani Pedrosa to go fastest in MotoGP's opening practice session at Indianapolis.
The Australian set his fastest time in the final minutes, and after a brief red flag period caused when Hector Barbera fell heavily at T16.
The Spaniard was riding for Pramac Ducati in a bid to prove his fitness, having broken his leg just four weeks ago. He had to be stretchered off the circuit and was taken to the medical centre and then the local hospital with chest and back pain. Pramac have 2010 Moto2 champion Toni Elias on standby.
Honda had controlled the session up until Barbera's incident, with Pedrosa clear on a 1m42.192s.
Stoner then managed to shave around two tenths off that after the resumption, dipping into the 1m41s.
No other rider was able to get within five tenths of a second of the Australian, with Ducati's Nicky Hayden leading the rest of the pack, 0.547s down.
His compatriot Ben Spies, facing possibly his final home MotoGP race - his future remains undecided - was fourth, a further tenth of a second down the road.
Stefan Bradl (LCR Honda) and Alvaro Bautista (Gresini) put the gloss on a strong session for Honda by finishing fifth and sixth respectively, ahead of Yamaha riders Cal Crutchlow (Tech 3) and championship leader Jorge Lorenzo.
Crutchlow was the only other man to fall during the session, losing his bike early on at T14. He recovered and was able to return in the final minutes, securing seventh.
That left him four spots above team-mate Andrea Dovizioso, with Lorenzo, Valentino Rossi and Barbera separating the pair.
Pos Rider Bike Time Laps 1. Casey Stoner Honda 1m41.925s 14 2. Dani Pedrosa Honda 1m42.106s + 0.181s 17 3. Nicky Hayden Ducati 1m42.472s + 0.547s 19 4. Ben Spies Yamaha 1m42.536s + 0.611s 17 5. Stefan Bradl LCR Honda 1m43.027s + 1.102s 20 6. Alvaro Bautista Gresini Honda 1m43.195s + 1.270s 19 7. Cal Crutchlow Tech 3 Yamaha 1m43.295s + 1.370s 17 8. Jorge Lorenzo Yamaha 1m43.312s + 1.387s 15 9. Valentino Rossi Ducati 1m43.345s + 1.420s 19 10. Hector Barbera Pramac Ducati 1m43.736s + 1.811s 12 11. Andrea Dovizioso Tech 3 Yamaha 1m43.745s + 1.820s 19 12. Yonny Hernandez BQR 1m44.328s + 2.403s 19 13. Aleix Espargaro ART 1m44.714s + 2.789s 18 14. Karel Abraham Cardion Ducati 1m44.739s + 2.814s 16 15. Mattia Pasini ART 1m44.913s + 2.988s 18 16. Randy De Puniet ART 1m46.298s + 4.373s 19 17. Ivan Silva BQR 1m46.332s + 4.407s 22 18. Michele Pirro FTR 1m46.480s + 4.555s 17 19. Colin Edwards Suter 1m46.520s + 4.595s 18 20. Steve Rapp APR 1m46.619s + 4.694s 13 21. Danilo Petrucci Ioda 1m46.941s + 5.016s 22 22. James Ellison ART 1m47.506s + 5.581s 21 23. Aaron Yates BCL 1m48.054s + 6.129s 15