Ryanair has only ever lost a plane once, due to a bird strike with only some injuries, and they are one of biggest airlines by number of flights (if not the biggest).

Turns out plane accidents are expensive, and the reputation loss as well. Don't even need to lose the plane, just the plane being stuck on the ground is expensive (they are also one of the most timely airlines because of this). Really can not afford to have accidents!

Cheap, safe, fast. You can have any 2 out of the 3.