Ever since the majorly heartbreaking reveal that Jack is dead on This Is Us, fans have (understandably) been losing their damn minds trying to figure out what Jack's possible cause of death could be. While there's been a slew of possible hints strewn throughout every episode of the show, as far as I see it, there's only one specific fan theory about Jack's death on This Is Us that you need to know about. And it's just as heartbreaking, and complex, as you'd expect from a show that so regularly delivers complex and heartbreaking storylines in every episode.
We've been seeing references to the issue throughout the show so far, and, frankly, it feels harrowing whenever the problem is brought up — and that issue is Jack's drinking habits. Though the show hasn't yet outright suggested that Jack has, or had, what could be considered to be a full blown addiction, a couple of episodes have dealt with the idea that the way in which the character uses alcohol is problematic and unhealthy.
After all, we were introduced to concerns regarding Jack's drinking problem early on in the series. Not only did we see Miguel lecturing Jack on his propensity to drink too much after work (and that his wife deserved better than that), but we also saw Rebecca dealing with his drinking habits directly, too.
After telling him that she wouldn't allow for alcohol to be a part of their home, he vowed to stop in order to be the best husband and father possible. Recently, however, we saw that vow being broken when Jack started drinking again following a huge fight between himself and Rebecca. What that scene appeared to sadly imply was the possibility that Jack may have never gotten over his dependence on alcohol, using drink as a crutch for when life became difficult. For many alcoholics, this can become an addictive cycle that is hard to break. But could it be the thing that actually kills Jack?
Obviously, excessive drinking can lead to various health problems such as liver disease, heart problems, high blood pressure, and strokes, all of which could put the character's life at risk far earlier than it should be. But Jack's drinking could have also led to a deadly accident. Specifically, it could be the case that Jack dies in a drunk-driving accident. And there's another fan theory regarding Jack's death that could definitely link up with this.
Due to the fact that Kate is afraid of flying on planes, and the time that Kevin mentioned he'd destroyed all of his model planes, many fans are speculating that Jack died in a plane crash. Which could definitely make sense. However, I've started to think that Jack may have died after being refused entry on a flight instead.
Airlines, after all, reserve the right to refuse passengers to board the plane if they appear too intoxicated to fly. There's every possibility, then, that Kate and Kevin's aversion to planes doesn't stem from their father dying in a plane crash, but instead his inability to board a plane that may have led to his death. After being refused access to board, Jack may have decided to drive to his destination instead.
And, considering the manner with which Kate appears to hold a certain amount of guilt for his death, I'd also speculate that he was trying to fly to Los Angeles to see her. And why? Perhaps to watch the Super Bowl with her, just as they used to enjoy back when Kate was a kid. Which would also bring the plot line of Jack's death full circle to the episode in which we first find out that Jack is dead (when Kate is watching the Super Bowl with her dad's ashes).
Still, that's just my opinion on the matter, and it might not hold true to what actually happens in the show. However, there's clearly more for us to discover concerning Jack's alcohol problem in the show, and there can be a lot of difficult consequences that come with such a dependence on alcohol. Hopefully, that's something that the show will explore in the detail and with the respect that it deserves.
Whether or not his potential alcoholism is the issue that eventually kills the character remains to be seen. But, even if it isn't, you can be sure it'll be a continuing bone of contention for Rebecca, and the rest of his family and friends, for episodes to come if he doesn't get a handle on it.