ABSTRACT
The definition is peculiar, as it puts together two concepts-namely, complexity and criticality-that can be defined independently. The motivation for presenting them together in SAE (1996) is obvious: airplanes are both complex and critical. We use this definition for the following reasons:
1. There is a steady trend toward the use of digital systems of increasing complexity in safety-critical applications. Systems need not be digital or complex to be safety critical: The Wright brothers invented and flew the airplane 12 years before Alan Turing was born. However, the flexibility and performance of digital technologies have greatly contributed to increasing their adoption in the safety-critical sector.
