ABSTRACT
Machines have a habit of failing. Fortunately, in the case of flying machines, it does not happen often. Nowadays, rarely does a system or component fail in flight and even if it does, more likely than not there will be a back-up or redundant system. In the case of vital components, there may be two redundant systems. In the past century, in terms of airline safety and reliability, aviation has progressed a long way.
