Marco Andretti notched the fastest time on Thursday in the first full day of practice for the 2009 Indianapolis 500.

Andretti topped the times with a speed of 362.871km/h on the famed 4km Indianapolis Motor Speedway oval, where the Indianapolis 500 will be held on 24 May.

More immediately, Thursday's practice was a warm-up for Saturday's scheduled pole position qualifying battle, with Andretti now apparently the man to beat.

"We really worked on the car the whole day," Andretti said. "The car was good to run with it.

"It's super-close out there, and it's going to be even closer as we go on. So hopefully we'll just build on what we did today."

Brazilian Helio Castroneves and Australian Ryan Briscoe, both driving for Penske, were next quickest, Castroneves clocking 362.483km/h and Briscoe 361.947km/h.

Defending Indy 500 champion Scott Dixon of New Zealand and his Ganassi teammate Dario Franchitti of Scotland - the 2007 winner - were fourth and fifth fastest, followed by England's Dan Wheldon.

Robert Doornbos of the Netherlands was the fastest rookie and seventh overall, while Danica Patrick, Graham Rahal and Australian Will Power rounded out the top 10.

Doornbos was keen on his chances in Saturday's qualifying, despite his newcomer's status. He is currently 13th in the IndyCar Series standings, the best of all the rookies.

"I seem to learn fast on the ovals, and the team is doing a good job, so I don't see why we shouldn't be in the top 11," Doornbos said of the grid positions on offer on Saturday.

Doornbos said qualifying for the Indy 500 is a world away from his previous experience of the circuit dubbed The Brickyard, which is celebrating it's centenary this year.

"Now, I already feel the history of the (oval) track with the brickyard and the speed down the straight," said Doornbos, who had driven as a Formula One test pilot on a different configuration of the circuit.

"I just love it," he added. "It wasn't intimidating at all as along as you respect the track.

"If you get to thinking you can be the fastest on the first day, you'll find yourself in the wall."

A crash by Ryan Hunter-Reay shadowed Thursday's practice, but the 28-year-old was cleared to resume driving after he was examined at the infield hospital.

Hunter-Reay, whose sixth place finish in the Indianapolis 500 last year made him the rookie of the year, spun exiting turn two and hit the outside wall.