Safety is an accumulation of knowledge about risk converted into practice, and no other mode of transportation has been as expansive as flying in incorporating what we know about the fallibility of humans and machines. As a result, the act of hurtling through the air at 500 mph six miles above the ground is less likely to result in your demise than almost any other type of travel. From the plane seats to the cabin air to the course and altitude of the flight, every decision in commercial aviation comes after careful consideration of its impact on safety. Here, in broad strokes, are the most significant.