Engines are a big one. But the reasons are innumerable. Commercial aviation is always scheduled, so you have a very definite takeoff time, location, and destina

Engines are a big one. But the reasons are innumerable. Commercial aviation is always scheduled, so you have a very definite takeoff time, location, and destination. This cuts down the variables encountered along the way greatly and allows for precise route planning taking weather and traffic into account at all times. Commercial flights are also 100% IFR even in perfect weather, which means their every maneuver is coordinated with ATC. ATP pilots are also literally 100x the experience of your average GA pilot with a couple hundred hours. Not only that but they are in regular practice, not just someone hopping in the left seat for potentially the first time in years. They're also held to a much higher medical clearance level by the FAA, so you have far fewer medical incidents inflight. GA also includes training flights too, which contribute a significant amount to the accident numbers.