Before Kyle Busch’s sudden death, fellow NASCAR driver Brad Keselowski had a grim encounter with him aboard a plane.

Busch, 41, was flying to Dover earlier this month when he and his rival had what Keselowski described as a “chance” run-in.

However, Busch — who ultimately died last week of severe pneumonia that progressed into sepsis — evidently wasn’t doing great during the flight.

“Kyle is normally a fairly gregarious person, very outgoing — and he wasn’t,” Keselowski told PEOPLE.

“He sat down one row behind me and next to me and fell asleep right away and I could tell he wasn’t feeling well.”

Busch’s last race was the NASCAR All-Star Race on May 17, in which he finished 17th and Keselowski finished 10th.

“And that was pretty much the last time I saw him,” Keselowski told People of their plane encounter. “We were in a race and you get in a race and you don’t really see each other. So I saw him on the racetrack.”

Prior to his death, Busch’s family announced that he had been hospitalized with a “severe illness.”

It had been mentioned on the May 10 broadcast of the Watkins Glen race that Busch was dealing with a sinus issue.

And sources later told the Associated Press that he became unresponsive while testing a racing simulator the day before his death.

Busch and Keselowski had been fierce rivals on the track, and the latter admitted he’d thought of what their relationship would be once their racing days were over.

“I guess I had visions before his death of… actually, I thought about this multiple times: What’s it going to be like when we’re both in the Hall of Fame and we’re doing some kind of ceremony together, whatever that might be?” he said to PEOPLE.

“Will the hatchet be buried? I think so. And will we actually be able to share a laugh about it? I guess in my mind, I hope so and now obviously not.”