From: https://www.faa.gov/space/compliance_enforcement_mishap

When does the vehicle-type involved in the mishap return to flight? A return to flight operations of the vehicle type involved in the mishap is ultimately based on public safety. The operator plays a significant role in the process to return to operations and is responsible for submitting a final mishap investigation report to the FAA for review and approval that details needed corrective actions. All required corrective actions must be implemented prior to the next flight unless otherwise approved. Based on the nature of the corrective actions, the operator may be required to submit either a license modification request or a new license application. These actions may occur concurrently. In summary, the FAA will not allow a return to flight operations until it determines that any system, process, or procedure related to the mishap does not affect public safety or any other aspect of the operator’s license. This is standard practice for all mishap investigations.