Gateway IndyCar: Will Power fastest as Penske dominates practice

In charge for much of the hour-long session, last week's Pocono winner Power eventually topped the timesheet with a 24.2521-second (185.551mph) lap.

Championship leader Josef Newgarden briefly held first place, but would finish second with a fastest time of 24.2635s.

Reigning champion Simon Pagenaud slotted into third, with Helio Castroneves - winner of the Gateway IndyCar race 14 years ago - rounding out the Penske rout in fourth.

The session suffered two caution periods, the first owing to a strange incident that befell Max Chilton.

The Chip Ganassi Racing driver lost control of his Dallara-Honda on pitroad and collided with a member of IndyCar personnel, who was knocked over but escaped serious injury.

This led to Chilton sitting out five minutes of practice as punishment. He went on to finish 14th.

Ed Jones put in a strong performance to finish fifth, 10 places ahead of returning Dale Coyne Racing team-mate Sebastien Bourdais. Gateway is Bourdais' first race back after being injured in his Indianapolis 500 qualifying crash in May.

The last two recent Indy 500 winners, Alexander Rossi and Takuma Sato, sandwiched seventh-placed Conor Daly.

The top 10 was rounded up by Scott Dixon and Ryan Hunter-Reay, the latter still in some discomfort from a huge shunt during qualifying last weekend at Pocono.

FP1 times