National Transportation Safety Board officials are investigating maintenance reporting procedures and inspection practices in connection with a fatal UPS MD-11 cargo aircraft crash that occurred in November, according to federal safety investigators.

The crash killed 15 people and has prompted NTSB officials to examine how damage was reported in the years leading up to the accident. Investigators are focusing on potential maintenance lapses that may have contributed to the fatal incident.

Witnesses testifying before investigators have indicated that a faulty aircraft component played a role in the crash. The testimony suggests that infrequent maintenance requirements may have been among the factors that allowed the defective part to remain undetected or unrepaired.

The NTSB's investigation is examining whether maintenance inspection schedules and reporting procedures were adequate to identify and address mechanical issues before they could lead to catastrophic failure. The agency has not yet released its final findings on the cause of the crash.

The November accident marks one of the deadliest cargo aircraft incidents in recent years. UPS operates one of the world's largest cargo fleets, and the MD-11 has been a workhorse of the international freight industry for decades.