how does luck (regarding getting a ticket) come into it.
The ticket analogy was meant to demonstrate that those with tickets usually always get to fly while late comers take their chances. In the same manner, being a baptized Christian who lives a life according to (without deliberate serious violations) the edicts -- has an automatic salvation. The ones who do not do this, but claim that they live good lives take their chances in that God may not agree with their assertions of living such good lives and therefore they may perhaps not be saved, not get a seat on the analog plane.
. . .can ensure fairness when good and bad in people ranges in a continuous spectrum.
We are told that the righteous shall automatically enter Paradise, once it is established, and that the unrighteous, those who were unaware of God's desires for mankind but still lived good moral lives will be given the chance to accept this by being entered Paradise to get the choice of living that life or to reject it. The wicked get an automatic eternal death sentence.
Since I am not the judge, there is only the knowledge that God judges fairly. Thus wickedness done deliberately and as a practice surely damns a person, believer or non-believer.
They also have the doctrine of universal salvation while ensuring fairness and justice for all actions of all people through consequential ethics of karma.
I can only tell you that we clearly are told that salvation is only through Christ. That God judges the ones not believers in him or Christ. Personally, I am barely hanging in there and could perhaps be damned if I give up. Thus, I am no better off than many, and you have to study things, make up your own mind on what you will do. All things have consequences, some eternal. Eternal sleep is not that terrible a choice, but life is better, if possible.