Understanding aviation acronyms used in operations is the key here. IOR stands for Initial Operations Report, the first formal document filed with operations to capture essential facts right after a flight or event. It provides immediate details like flight identifier, equipment, times, weather, and any observed issues so the team can coordinate follow-up actions, maintenance, or investigations. The other phrases describe different types of documents or purposes—an Operational Review implies later evaluation rather than a first-report format, In-flight Operations Record sounds like a log kept during the flight rather than an initial report, and an Onboard Report would focus on the onboard reporting process rather than the formal operations document. Since IOR matches the initial, factual report used to kick off subsequent steps, Initial Operations Report is the correct meaning.