Answer:
You calculate the statistical probability of dying in a plane crash in the same way that you calculate the probability of anything else. You simply divide the number of expected outcomes by the number of possible outcomes.
To determine the statistical probability of dying in a plane crash, you divide the number of people that have died in a plane crash by the number of people that have flown in planes. You can aggregate this anyway you want, over whatever period of time you want, so long as you properly state the conditions under which you perform your calculation.