This report is the first of a series of three which, within Phase 1 of the Human Error in ATM (HERA) Project, deals with how human errors in Air Traffic Management (ATM) can be analysed to improve safety and efficiency in European ATM operations. The purpose of this work is to increase the effectiveness of error recording, analysis and prevention. This first report reviews the theoretical and practical techniques from other industries, from general psychology, and from the few ATM-oriented approaches that have been developed so far. This review culminates in a conceptual framework, which will be the basis for a detailed methodology for analysing and learning from error-related incidents in ATM. A shorter management summary of this report is also available (EATMP, 2002a).