This paper addresses a significant gap in competency-based training and assessment (CBTA) for aviation personnel. While the International Civil Aviation Organization (ICAO) has established competency models for various roles, including air traffic controllers, a model for air traffic management officers (ATMOs) - a relatively new role evolved from air traffic controllers - remains undeveloped. This study aims to develop a competency model for ATMOs. We employed the behavioral event interview (BEI) protocol to gather critical incidents from active ATMOs. A team of subject matter experts then analyzed these incidents from multiple perspectives to identify essential competencies for ATMO roles. The research culminates in the novel presentation of a comprehensive competency model for ATMOs, filling an important void in aviation personnel training standards.