In two empirical studies using desktop flight simulators, pilots were monitored while following procedures. In both experiments, pilots demonstrated a high degree of reliance on rule-based heuristics for following procedures (techniques), rather than on the procedures themselves. This was true regardless of the resulting compliance with the procedure. Changes to the procedure and changes to the content of displayed information had no effect on the use of techniques. In addition, frequent instances of noncompliance to procedure were recorded. The most common types of noncompliance, technical failures in implementing the procedure, were found to be nearly all innocuous, while failures related to a lack of situation awareness comprised the bulk of unsafe instances of noncompliance. Also found were a number of instances of noncompliance which actually enhanced the safety of the procedure. The results have implications for the design of procedures and for automated aids for procedure following.