What are some of the realizations about loss and the idea of safety that are prevalent today?

It has been said that history is a good teacher. How has the concept of aviation safety changed over the past 100 years? What are some of the realizations about loss and the idea of safety that are prevalent today?
Your short papers must demonstrate a comprehension of the issue based on facts, not opinion. Facts may be from the course material or other stated references. Use terms associated with aviation safety and program management, associate any concepts behind System Safety Management (SMS), and relate any basic safety management concepts to safety programs while answering the question.