Investigation Summary
The investigation into Flight 23 was led by Melvin Purvis of the United States Bureau of Investigation and involved forensic experts from Northwestern University. Physical evidence at the crash site provided clear indicators of a deliberate explosion rather than a mechanical failure: the toilet and baggage compartment were found shattered into fragments, with metal shards embedded in the interior side of the toilet door while the exterior remained clean. This pattern indicated a high-pressure blast originating from within the cargo area. Furthermore, the aircraft's gasoline tanks were found crushed inward, proving they had not exploded but were instead collapsed by the external force of the blast. Investigators recovered a rifle and a suspicious brown package from the wreckage, but both were eventually ruled out as the source of the explosion. The tail section was found nearly a mile away from the main wreckage, confirming a mid-air structural failure caused by the detonation.
Final Conclusions
The investigation concluded that the crash was caused by a nitroglycerin-based explosive device placed in the rear baggage compartment. The FBI declassified 324 documents related to the case in 2017, which reaffirmed the findings of sabotage but noted that the perpetrator's identity and motive remain unknown. The case is officially classified as an unsolved act of air sabotage.
Video Analysis
No video analysis linked for this case file yet.
Systems & Failure Modes
Baggage Compartment
Located in the rear of the aircraft, this area was the site of the explosion that caused the structural failure of the empennage.
Empennage
The tail section of the aircraft was completely severed from the fuselage by the force of the nitroglycerin blast.
Interesting Facts
- 01This was the first proven instance of air sabotage in the history of commercial aviation.
- 02The explosive used was identified as nitroglycerin.
- 03The tail section was severed by the blast and found approximately one mile from the main crash site.
- 04Stewardess Alice Scribner was the first United Airlines stewardess to die in an aircraft crash.
- 05The Boeing 247 was a state-of-the-art aircraft for its time, featuring all-metal construction and retractable landing gear.
Safety Actions & Advisories
Security Protocols
The incident prompted the aviation industry to consider preliminary forms of passenger security screening and stricter cargo handling procedures.
Known Controversies & Unanswered Questions
Alternative Theories of Destruction
Reference ↗Before forensic evidence confirmed a nitroglycerin blast, various theories were proposed including a fuel leak, structural failure, or a lightning strike. Some early speculation also focused on a passenger carrying a brown package or a rifle, though both were eventually ruled out by investigators.