DAYTONA BEACH, Fla. — William Byron launched Hendrick Motorsports’ 40th anniversary season by snapping the team’s nine-year Daytona 500 losing streak with a win Monday in the rain-delayed “Great American Race.”

Byron crossed under the white flag denoting the final lap at the exact moment a crash broke out behind him. The caution flag was thrown and he wasn’t quite sure if he was the official winner as he circled Daytona International Speedway one final time.

“That was a long lap and a half,” Byron admitted. “My crew chief tried to speak up and he was all emotional, so I thought, ‘Man, I hope he knows because I don’t know if we won this race.'”

The last Hendrick driver to win the Daytona 500 was Dale Earnhardt Jr. in 2014. The 26-year-old from Charlotte, North Carolina, is the sixth different driver to win the 500 for Rick Hendrick, the winningest team owner in NASCAR history who made his way to victory lane on the actual 40th anniversary of his first Cup win.

“The first time we came here, we didn’t think we had any business even being here,” Hendrick said in victory lane. “We felt way out of our league. Now here we are 40 years later. You couldn’t write the script any better. To win this on the 40th, to the day, it’s just awesome.”

The ninth Daytona 500 win for Hendrick Motorsports tied the team with Petty Enterprises for most in NASCAR history.

“William Byron was already a superstar, and I mean, he just went to another level of being superstar,” said Hendrick vice chairman Jeff Gordon, himself a three-time Daytona 500 winner in the No. 24 Chevrolet.

“I wasn’t driving the car, but I felt like I was making every lap out there with him. We’re going to celebrate. This is a huge win.”

Byron, who had never finished higher than 21st in the Daytona 500, is a self-taught racer who used computer equipment to hone his skills. He made it to the championship last season when Byron won a career-high six races, but lost out on the title to Ryan Blaney, older brother of Byron’s longtime girlfriend.

“I’m just a kid from racing on computers and winning the Daytona 500, I can’t believe it,” Byron said. “I wish my dad was here. He’s sick, but this is for him, man. We’ve been through so much, and we sat up in the grandstands together and watched the race.”

The fourth and final caution of the race began when Hendrick driver Alex Bowman hit Byron from behind and it caused Byron to sideswipe Brad Keselowski and trigger a 23-car crash that caused a red flag that lasted more than 15 minutes.

There were four laps remaining on the final restart and Byron was in second in the No. 24 Chevrolet. He and Ross Chastain of Trackhouse Racing pushed back and forth for the lead and it was Byron out front as a crash broke out behind him just as he’d crossed under the white flag marking the final lap of the race.

Byron won under caution and was followed by teammate Bowman in a sweep for Chevrolet. Christopher Bell in a Toyota for Joe Gibbs Racing finished third and was followed by Chevys from Corey Lajoie of Spire Motorsports and AJ Allmendinger of Kaulig Racing.

Bubba Wallace was sixth in a Toyota for 23XI Racing and was followed by John Hunter Nemechek in another Toyota but for Legacy Motor Club. Chase Briscoe was eighth in a Ford for Stewart-Haas Racing and followed by Legacy driver Erik Jones and SHR teammate Noah Gragson.

The race ran one day later than scheduled because of persistent rain all weekend at Daytona International Speedway. Monday was supposed to open with the rescheduled second-tier Xfinity Series race and then lead into the 500, but when it was still raining Monday morning, NASCAR reordered the events and made the Xfinity race the closer.

Joey Logano started from the pole in a Ford for Team Penske — a first for Roger Penske’s storied team — in an all-Ford front row. Right before the race began, three-time Daytona 500 winner Denny Hamlin became the betting favorite, according to FanDuel Sportsbook.

There was no pre-race concert Monday as scheduled performer Pitbull said he’d return next year to make good on his appearance. He said a scheduling conflict prevented him from staying in Daytona on Monday, but grand marshal Dwayne “The Rock” Johnson did stay the extra day and was the most popular attraction in pre-race activities.

Johnson was swarmed on the starting grid and in the fan zone and received the loudest ovation in the pre-race driver meeting, to which he showed up 30 minutes ahead of schedule wearing a black tank top.

The flexibility NASCAR has shown this month in working within its schedule to avoid inclement weather is practically unprecedented in the first 75 hours of the series. NASCAR, to start the month, moved the exhibition Clash at the Coliseum up a full day because of impending rain. At Daytona, it rescheduled the ARCA Series race from Saturday to Friday night, and made early decisions to move both the Xfinity and Cup Series races.

The decision to postpone the Cup race a day was made early Sunday morning and prevented fans from sitting in rain-soaked grandstands to see if the race would begin.

Just hours later, teams used Sunday’s rain delay to reveal to The Associated Press that they have hired one of the country’s top antitrust and sports lawyers to advise them in their ongoing dispute with NASCAR over a new revenue-sharing model.

The decision to hire Jeffrey Kessler, partner and co-executive chair of Winston & Strawn LLP, followed a meeting at Daytona that included the majority owner from every chartered team. Although the teams invited NASCAR representatives to attend, none did.

Kessler’s hiring was revealed to AP by the five members of the team ownership negotiating committee. It comes amid a breakdown in negotiations between teams and NASCAR that led the 36 chartered teams to decline last month to extend their exclusive negotiating window with the sanctioning body on the existing deal.