When must an operator file an NTSB report for an incident?

An operator must file a report with the National Transportation Safety Board (NTSB) when requested. This means that while the operator may need to be prepared to report incidents, the actual requirement to submit a report only comes into play upon request from the NTSB. The NTSB investigates significant aviation incidents and accidents, and they will request reports when deemed necessary for their investigation process.

Filing a report on the specific timelines as indicated in the other options might imply a misconception about the requirements. Option indicating a timeframe may suggest that reports must be filed proactively within a specified period, but in the case of an NTSB report, the obligation to file is primarily tied to a request from the board. Understanding the process helps in grasping the regulatory framework surrounding aviation safety and incident reporting.