Some consequences of application of current damage tolerance airworthiness requirements for transport aircraft are discussed in terms of designing stiffened-skin structures for safety under all operational load conditions. Compliance with these requirements can be shown by analysis supported by test evidence. To provide the designer with analytical tools to demonstrate that his design meets the required residual strength and crack propagation properties, a number of computer routines were developed by the National Aerospace Laboratory. The principles underlying the calculation procedures used in these computer programs are discussed. An approach incorporated in the computer programs to predict the residual strength of stiffened panels with a skin of a ductile material (such as 2024 alloy) is included. Applications of these programs to some practical stiffened-skin structures are presented together with analysis-test correlations.