Although spaceflight evidence regarding cohesion and performance is limited by the scarcity of objective team performance data, case studies, interviews and surveys have been conducted within the spaceflight community that have provided evidence that issues pertaining to cohesion exist and are perceived as threats to effective operations. For example, breakdowns in team coordination, resource and informational exchanges, and role conflicts (all common indicators of poor team cohesion) were mentioned as contributors to both the "Challenger" and the "Columbia" space shuttle accidents. Likewise, interviews and surveys of flight controllers indicate that mission teams are commonly concerned with team member coordination and communications, and that interpersonal conflicts and tensions do exist.