I would have thought that the list would be
- very reliable and mission-capable, powerful, fully de-iced aircraft, which can outclimb 99% of hazardous weather and has radar to avoid the stuff it can't outclimb immediately
- most routes flown between straightforward airports
- high level of cockpit automation AND it gets used all the time
- the airline best known for very tight timing (Ryanair) operates brand new (very low downtime) aircraft
- well organised crew training and recurrent training
One could argue about any of the above but take out any one point and see how it stacks up. It won't.