Analysis of information sources in references of the Wikipedia article "Flight recorder" in English language version.
The NTSB sent the cockpit voice recorder (CVR) and flight data recorder (FDR) to their labs. They will use data from the FDR to narrow down the area to search for the door plug. However, the CVR was completely overwritten, meaning there is nothing on the CVR. The CVR overwrites every two hours.
The Nigeria Civil Aviation Authority (NCAA) had noticed that some airline operators' flight crew members were in the practice of continuously overwriting the CVR information after an occurrence. This practice makes it practically impossible for the Nigerian Safety Investigation Bureau (NSIB) to retrieve actual data to aid in its investigation
airlines indulge in the unprofessional act in order to circumvent investigation by the Nigeria Safety Investigation Bureau (NSIB).[...] safety managers stated that some airlines have consistently indulged in this unwholesome practice, which could impact safety negatively. The NCAA and the NSIB had in the wake of the report of the incident involving Max Air's B747 incident expressed concern over the incessant occurrence of the issue with airlines.
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