Tony Kanaan was quickest in morning practice for the Iowa Speedway round of the IndyCar Series.
In a strong session for Andretti Autosport, the Brazilian hit the front early and stayed there until a late caution for debris caused a slightly premature end. His team-mate Marco Andretti was third, the duo split by Penske's Will Power.
Ganassi duo Scott Dixon and Dario Franchitti completed the top five in an uneventful session, while Panther's Dan Wheldon was sixth.
A further hour-long practice takes place this afternoon prior to qualifying.