With the arrival of Memorial Day weekend, the 99th running of the Indianapolis 500 is Sunday.
Scott Dixon, a former Indy 500 winner and three-time series champion, will lead the 33-car field from the pole position at Indianapolis Motor Speedway.
Alongside Dixon in the Indy 500's unique three-wide starting format will be Team Penske drivers Will Power and Simon Pagenaud.
There have been five different winners in the first five races this season in the Verizon IndyCar Series. But all of those races were on twisty street or road courses. This is the series' first race of the year on a high-speed oval.
Here are four things to watch as IndyCar holds its most celebrated race, which draws more than 200,000 spectators:
Safety concerns: The cars of three drivers went airborne in crashes during practice this month, prompting IndyCar to make quick changes.
The series slowed down the cars for qualifying after the incidents involving Helio Castroneves, Josef Newgarden and Ed Carpenter. None of the drivers was hurt.
The two manufacturers in the series, Chevrolet and Honda, supplied their teams with new body styles, or "aero kits," this season. All three of the cars that went airborne were Chevys. But it's unclear whether the new bodies played a role in the cars flipping into the air.
There were no similar incidents during qualifying last weekend for the Indy 500. But in practice Monday, James Hinchcliffe suffered a serious upper-thigh injury when his Honda-powered car slammed into the wall and nearly got airborne as it spun to a stop.
Hinchcliffe, who won earlier this year in New Orleans, required surgery and is probably out for the season. He had qualified 24th for the Indy 500. Ryan Briscoe will replace him Sunday in the No. 5 car for Schmidt Peterson Motorsports.
The field will have a final, one-hour practice Friday.
Dixon the betting favorite: The reserved New Zealander known as "The Iceman," who drives for Chip Ganassi Racing, won the Indy 500 from the pole in 2008, the same year he won one of his IndyCar titles.
The 34-year-old driver also has a victory this year, at the Toyota Grand Prix of Long Beach in April.
Dixon is all-business at the race track, and right now he seems formidable if his team deftly handles his pit stops and fuel strategy and Dixon avoids any crashes.
Gamblers like his chances. Dixon was the favorite to win the race Sunday, at 9-2 odds, on the sports betting website Bovada.com. Pagenaud and Power were next at 11-2.
"We're starting in the right place but it's a long race," Dixon said. "Hopefully, we can replicate what we did in 2008."
Penkse's momentum: Penske drivers Juan Pablo Montoya, Power and Castroneves are 1-2-3, respectively, in the IndyCar championship point standings.
Power won the series' most recent race, on the road course at Indianapolis. Montoya, a former Indy 500 winner, won this season's opener on the streets of St. Petersburg, Fla.
Castroneves, who recently turned 40, is a three-time winner of the Indianapolis 500. He starts fifth Sunday.
Castroneves' bid for a fourth win at the Brickyard fell just short last year when he lost to Ryan Hunter-Reay by less than a car length in the second-closest Indy 500 finish in history.
Finally, team owner Roger Penske has a record 15 wins at the Indy 500.
But all of this guarantees nothing. It's been six years since a Penske driver last captured the race, with Castroneves at the wheel in 2009.
Jeff Gordon lends a hand: The four-time NASCAR champion will drive the pace car for the Indy 500, then rush to Charlotte Motor Speedway in North Carolina to race in NASCAR's Coca-Cola 600 on Sunday night.
Gordon was born in California but grew up in the Indianapolis area, his goal at one point being an IndyCar racer.
He chose NASCAR stock-car racing instead, where he's became one of its legendary drivers. He's also a record five-time winner of NASCAR's Brickyard 400 that's held at Indianapolis Motor Speedway in the summer.
What: 99th Indianapolis 500.
Where: Indianapolis Motor Speedway.
When: Sunday, 9 a.m. PDT.
Track: 2.5-mile rectangular oval (200 laps).
Defending winner: Ryan Hunter-Reay.