DAYTONA BEACH, Fla. (AP) — Dale Earnhardt Jr. traded in his T-shirt, jeans and sneakers for a head-to-toe pilot uniform, climbed up the portable stairs and slipped into the cockpit of the iconic Goodyear Blimp.

He kept his head down and turned away from a 65-year-old military veteran who thought he was onboard for a once-in-a-lifetime ride. Retired Marine Corps sergeant major Paul Siverson settled into his seat near Earnhardt — unbeknownst that his "first, second and third favorite NASCAR driver" was at the controls of the 246-foot helium-filled airship.

When Earnhardt turned and said hello, Siverson jumped in delight.

"Been talking about you all week," Siverson said.

Everyone has, really.

Earnhardt is the biggest story of Speedweeks. While it's fairly common for the two-time Daytona 500 winner to be the center of attention at Daytona International Speedway, especially given his father's fame and tragic fate at the superspeedway, it's been considerably different this year.

All those cheers have been joined by fears.

NASCAR's most popular driver missed 18 races, half the season, in 2016 because of lingering concussion symptoms that included nausea as well as vision and balance issues.

He struggled to keep his eyes focused while simply riding in a car last July. During a ride from his home to Raleigh, North Carolina, to taste wedding food with his then-fiancee Amy, he couldn't look out the windshield. He had to stare at the floor for two hours each way.

He would pick something on a wall to focus on, but couldn't keep it in sight once he started taking a few steps.

"I could go sit on my couch and convince myself I was 100 percent," he said. "That was my comfort zone. Nothing was happening there. No anxiety. Anytime I went out in the world, any little bit of anxiety would make everything crazy. ... I couldn't put one foot in front of the other without falling over like a drunk-driving test."

Forget racing. Sudden movement, loud noises and busy places all made Earnhardt cringe.

Even in November, after months of treatment and recovery, Earnhardt went hunting with friend and fellow driver Martin Truex Jr. and would stumble to one side or the other after five or six steps.

But that was progress, albeit minor, and it continued every day for the next month.

His vision cleared. His ability to focus returned. He slowly started feeling better, and by early December, he was back in a race car and had gained medical clearance to return this season.

Now, he's back at Daytona, back in the No. 88 Chevrolet and back at the front of the field. Earnhardt was second in pole qualifying last Sunday, meaning he will start on the front row for the Daytona 500 for the fourth time in his career. He also was scheduled to start one of the twin qualifying races Thursday from the pole.

The real test will be after that first head-jarring crash.

"I don't want to wreck to sort of quantify my recovery," he said. "I think, though, should that happen and I come out the other side feeling great, that will add a ton of confidence. I can't sit here and say I know exactly how I'm going to react in those situations with confidence. So yeah, when I go through that process, there's a box or two to check that aren't yet (checked)."

Earnhardt sat down with NASCAR officials recently to go over details about the inside of his car, specifically about how and where his headrest is mounted. He estimates having at least five diagnosed concussions during his 18-year Cup career.

"Am I nervous at all about it? I'm nervous about it until I get in the car," he said. "When I get into the car, I can't have any concern. I can't have any worry or fret, or I'll drive completely different. ... I know what a result I can get by driving without fear, and I know what kind of result I can get if I have even a sliver of apprehension. I won't be able to win the race. Once you second-guess yourself one time, it snowballs and it just continues throughout the rest of the race."

At least publicly, there has been no second-guessing of Earnhardt's decision to get back in a race car.

"Well, I hope he's competitive and he goes out there and has fun because he sure is fun to talk to these days," retiring driver and former teammate Michael Waltrip said. "He's just really energetic and really open and honest and is really cool to be around. He's always been cool to be around if you know him, but it seems like he's opened up to the world more, and so to see him go out there and win a race, I'd like to see that happen."

Earnhardt has 26 victories in NASCAR's top series, but he's still chasing that first championship. He created a stir this week when he told "The Dan Patrick Show" he would consider retirement if he won the title. After a day to reflect on something he initially said was a tongue-in-cheek statement, it started to sound like the perfect exit strategy for a 42-year-old driver who just got married and wants to start a family.

"I didn't expect people to be like, 'Seriously? You really mean that?'" he said. "Yeah, if you want to really think about it, God almighty, yeah. If I retire and won this championship, it's be hard not to spike the football on stage at Vegas and call it a career. Why not?

"There's still a lot about it that I haven't done just the way I want to do it. I want to learn how to enjoy it all the way, fully. I've got a couple more years that I'd like to keep going. But, dang, yeah, if I won a championship, shoot, that's the motivation for me in competing. Once that's checked off the list, that'd be everything."

With so much attention focused on Earnhardt, he's been the busiest driver in the garage this week.

He did a media tour in New York City on Tuesday, was bombarded with questions at Daytona 500 media day and then traveled to nearby New Smyrna Beach Airport for the Goodyear Blimp surprise.

Earnhardt spent close to two hours in and around the blimp and getting to know Siverson and his 47-year history of service. Siverson retired after 30 years in the Marine Corps in 2000 and now helps other veterans at NCServes in Jacksonville, North Carolina. Earnhardt presented Siverson with a $10,000 check from Goodyear for the charity.

Earnhardt, who had never been in a blimp, even joked about bringing home a keepsake from the experience.

"I'm going to keep this outfit for Halloween," he said.

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This version corrects Earnhardt's from 41 to 42.