I just finished seeing the movie.
The accident was not his doing in his state of drunkeness, but was due to a long neglected maintenance issue.
Despite being drunk while piloting, his innate and instintive skills of piloting, made him take the decisions that he did which saved bulk of the lives.
However, had he lied and got himself exonerated, he realised, he would probably cause much severe damage, as a pilot, in the future. This realisation, in my opinion, and his core humane character made him accept his shortcomings openly which gave him redemption which he sought for a long time but couldn't bring himself to face.
Nice and touching movie.