Sebastien Bourdais opened IndyCar's inaugural visit to the Indianapolis Motor Speedway road course by going fastest in the first practice session.
The KV driver had been the pacesetter during the opening phase of the session, and leapt back to the top just under two minutes before the chequered flag with a 1m10.9335s effort.
He improved on that next time around for a best time of 1m10.5150s, leaving him a comfortable 0.3903 seconds clear of Andretti's Ryan Hunter-Reay.
Simon Pagenaud, who had also enjoyed a stint at the top of the timesheets, finished the morning third-fastest ahead of Josef Newgarden; the Sarah Fisher Hartman racer having recovered from an early spin into the Turn 4 gravel that prompted a spell under reds.
Reigning series champion Scott Dixon rounded out the top five.
Another driver who had led the session early on was Will Power, although the Penske driver did not make the same gains as many of his rivals during the final 20 minutes and he finished up 11th-fastest.
Aside from Newgarden's spin the session was interrupted just once, although the second red flag had nothing to do with an incident on the track: the cars were called back to pitlane due to a brief power failure in race control.
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Pos Driver Team/Engine Time Gap 1. Sebastien Bourdais KV/Chevy 1m10.5150s 2. Ryan Hunter-Reay Andretti/Honda 1m10.9053s +0.3903s 3. Simon Pagenaud Schmidt/Honda 1m11.0045s +0.4895s 4. Josef Newgarden Fisher/Honda 1m11.0188s +0.5038s 5. Scott Dixon Ganassi/Chevy 1m11.0454s +0.5304s 6. Mikhail Aleshin Schmidt/Honda 1m11.1011s +0.5861s 7. James Hinchcliffe Andretti/Honda 1m11.1365s +0.6215s 8. Ryan Briscoe Ganassi/Chevy 1m11.1932s +0.6782s 9. Carlos Munoz Andretti/Honda 1m11.1973s +0.6823s 10. Jack Hawksworth Herta/Honda 1m11.2059s +0.6909s 11. Will Power Penske/Chevy 1m11.2115s +0.6965s 12. Sebastian Saavedra KV/Chevy 1m11.2681s +0.7531s 13. Helio Castroneves Penske/Chevy 1m11.3530s +0.8380s 14. Justin Wilson Coyne/Honda 1m11.3875s +0.8725s 15. Marco Andretti Andretti/Honda 1m11.4210s +0.9060s 16. Carlos Huertas Coyne/Honda 1m11.4225s +0.9075s 17. Juan Pablo Montoya Penske/Chevy 1m11.5309s +1.0159s 18. Oriol Servia Rahal/Honda 1m11.5606s +1.0456s 19. Graham Rahal Rahal/Honda 1m11.6178s +1.1028s 20. Tony Kanaan Ganassi/Chevy 1m11.6328s +1.1178s 21. Franck Montagny Andretti/Honda 1m11.6620s +1.1470s 22. Martin Plowman Foyt/Honda 1m11.6926s +1.1776s 23. Charlie Kimball Ganassi/Chevy 1m11.6952s +1.1802s 24. Takuma Sato Foyt/Honda 1m11.9870s +1.4720s 25. Mike Conway Carpenter/Chevy 1m12.0910s +1.5760s