Marc Marquez kicked off the Indianapolis MotoGP weekend with a commanding fastest time in opening practice.
The championship leader spent much of the session batting for the top spot with his sometime Moto2 title rival Stefan Bradl.
The German, who sealed a new LCR Honda deal at the start of the weekend, managed to depose factory Honda man Marquez from first place several times in the first part of the morning.
In the end Marquez stamped his authority on the session with a 1m40.781s, putting him half a second clear of the pack at that pack.
Cal Crutchlow ultimately emerged as his closest rival. A 1m41.081s from the Briton as he took the chequered flag moved his Tech 3 Yamaha to second, exactly three tenths off Marquez.
World champion Jorge Lorenzo had a spell on top and ultimately beat Bradl to third place on his Yamaha.
Lorenzo's team-mate Valentino Rossi edged out Alvaro Bautista and Dani Pedrosa for the final top-five place.
Nicky Hayden was top home rider in ninth, just behind his Ducati team-mate Andrea Dovizioso.
Hayden's countryman Ben Spies began his MotoGP comeback with a solid 11th place.
The 12 prototypes filled the top 12 positions, meaning CRT pacesetter Aleix Espargaro had to settle for an unusually low 13th.
Yonny Hernandez was the second-quickest CRT for Paul Bird despite having to abandon his primary bike following a minor fall.
The biggest accident of the session befell Karel Abraham. The Czech rider is being treated for a potential shoulder injury having landed badly in a high-side at Turn 10 early on.
Pos Rider Team Time Gap Laps
1. Marc Marquez Honda 1m40.781s 19
2. Cal Crutchlow Tech 3 Yamaha 1m41.081s +0.300s 18
3. Jorge Lorenzo Yamaha 1m41.261s +0.480s 18
4. Stefan Bradl LCR Honda 1m41.424s +0.643s 20
5. Valentino Rossi Yamaha 1m41.547s +0.766s 21
6. Alvaro Bautista Gresini Honda 1m41.571s +0.790s 18
7. Dani Pedrosa Honda 1m41.590s +0.809s 19
8. Andrea Dovizioso Ducati 1m41.793s +1.012s 19
9. Nicky Hayden Ducati 1m41.830s +1.049s 20
10. Bradley Smith Tech 3 Yamaha 1m42.405s +1.624s 21
11. Ben Spies Pramac Ducati 1m42.507s +1.726s 18
12. Andrea Iannone Pramac Ducati 1m42.745s +1.964s 19
13. Aleix Espargaro Aspar Aprilia 1m42.866s +2.085s 14
14. Yonny Hernandez PBM Aprilia 1m43.088s +2.307s 11
15. Colin Edwards Forward FTR-Kawasaki 1m43.570s +2.789s 17
16. Karel Abraham Cardion Aprilia 1m44.009s +3.228s 5
17. Randy de Puniet Aspar Aprilia 1m44.125s +3.344s 18
18. Claudio Corti Forward FTR-Kawasaki 1m44.316s +3.535s 19
19. Danilo Petrucci Ioda-Suter-BMW 1m44.395s +3.614s 22
20. Hiroshi Aoyama Avintia FTR-Kawasaki 1m44.606s +3.825s 17
21. Hector Barbera Avintia FTR-Kawasaki 1m44.698s +3.917s 18
22. Lukas Pesek Ioda-Suter-BMW 1m45.379s +4.598s 19
23. Bryan Staring Gresini FTR-Honda 1m45.527s +4.746s 20
24. Michael Laverty PBM-Aprilia 1m45.688s +4.907s 18
25. Blake Young Attack APR-Kawasaki 1m47.770s +6.989s 15