From a pure game play perspective, the game engine is built on a system of probabilities that are impacted by variables. In the case of technical problem with an aircraft, if all variables are perfect (i.e. brand new plane, 100% condition, etc), there will still be a chance (albiet, a lesser chance) for you to end up with a tech delay/cancellation depending on the computerized equivilant of rolling the dice. I.e. you roll snake eyes in that scenario, you're delayed. If you hve a crap plane, perhaps only boxcars will keep you from getting delayed.