Indianapolis 500: Penske's Simon Pagenaud leads Thursday practice

The Team Penske driver secured the top of the speed charts with a fastest lap average of 228.793mph.

"Today was a really good day," Pagenaud said. "We've been focusing on understanding what the car does in qualifying runs.

"Very happy to see the preparation from Penske and how fast the #22 car is. So far, so good."

Andretti's Carlos Munoz was second-fastest at 228.126mph ahead of Ganassi trio Sage Karam, Scott Dixon and Tony Kanaan.

"Today we were really just focusing on pack racing and long runs with my team-mates," said Munoz.

"The car feels really comfortable - I'm really happy. I feel that I'm competitive, more competitive than last year.

"Now for tomorrow, we're going to focus on qualifying and see where we are speed-wise."

Josef Newgarden was at the centre of the only major incident of the day when his car snapped backwards and hit the wall at Turn 1 before launching into the air and landing upside-down. The CFH driver was uninjured.

Elsewhere, Simona de Silvestro returned to the track after losing two days to repairs following the fire that damaged her Andretti car earlier in the week.

"Today we ran mostly in traffic," she said. "We learned a lot. I have a little bit of work to do, and I'm looking forward to going back out there tomorrow and working on it."

The day also marked Tristan Vautier's return to an IndyCar cockpit for the first time since 2013; the Frenchman completing his refresher in the wake of his call-up to qualify Dale Coyne Racing's #19 car for James Davison, who has a scheduling conflict this weekend.

It also featured the first shakedown laps of the month from Buddy Lazier, who became the 34th entry to put a car onto the track ahead of qualifying on Saturday and Sunday.

THURSDAY RESULTS:

* Hinchcliffe drove both his own car (28th) and team-mate Conor Daly's (31st)