EU agencies have become important regulatory venues. Initially established to provide expert advice, many have gained far-reaching decision-making and enforcement powers. This has attracted considerable attention from stakeholders, but the extent of their influence on EU agency conduct has remained a black box. We employ a novel dataset of 203 consultations (2007-2017) containing 26,468 attempts of stakeholders to change proposed regulatory rules by the European Union Aviation Safety Agency, as well as the agency's response. This dataset allows for an original approach to measuring influence by linking influence attempts to rule changes. We found that business interests are far more influential than diffuse public interests. This has important implications for the legitimacy of EU agency stakeholder policies, as they are meant to make EU agencies more broadly accessible. National regulators are also influential in EU agency consultations, pointing to the unacknowledged importance of stakeholder consultations for EUnational regulator interactions.