I think winning can probably only feel satisfactory if it's the result of an actual deliberate decision. In my case I figured I had gotten most of the information I needed from the first playthrough, which is the only reason why I didn't talk to the flight attendant on the second attempt. So maybe what you need to do is have some sort of incentive for players to talk to the flight attendant (maybe to get an item?) so they think they need to do it again on subsequent playthroughs, so that not talking becomes more of an active choice?
Also, maybe I should mention that when I was operating on the assumption that there was still a "real ending" to try to achieve, I assumed that the issue was that I would need to be the one to deliver the energy drink to the captain (i.e. maybe the captain needs an energy drink *but also* something else needs to happen that requires the flight attendant to be distracted). It also wasn't clear to me that talking to the captain directly causes a crash by distracting him, since I only got into the cockpit right as the 10 mins were expiring, so the captain fell asleep while talking to me. So I assumed I would be able to give him the energy drink once inside the cockpit, although this proved to be false on a subsequent playthrough. (I did notice the cockpit slowly tipping once I entered, but then the captain visibly falling asleep overrode the idea that I had directly caused the crash by entering the cockpit).
Hopefully that provides some insight into my thoughts/interpretation of what I was seeing.