At 7:03 p.m. on November 1, 1955, United Airlines Flight 629 disintegrated in midair after a brilliant flash witnessed by air-traffic controllers. It had departed Denver only 11 minutes earlier for Portland, Oregon.
Thirty-nine passengers and five crew members died. Wreckage from the DC-6B was scattered across six square miles of farmland in Weld County, Colorado.
Investigators determined that the aircraft began to fragment near its tail. After detecting the odor of explosives in a baggage compartment, they located pieces of sheet metal bearing trace chemical byproducts associated with dynamite.
Background checks led investigators to passenger Daisie Eldora King and her son, John Gilbert Graham. Bomb-making components were recovered during a search of Graham's home. Less than two weeks after the crash, he confessed to placing a dynamite bomb in his mother's luggage.
No federal statute then specifically made detonating a bomb aboard an aircraft a crime. Graham was charged locally with one count of first-degree murder, convicted and executed in Colorado in 1957. The investigation later featured in the 1959 film The FBI Story.
Flight 629, however, was not the first commercial airliner believed to have been brought down by sabotage. That distinction belongs to a disaster 22 years earlier, on October 10, 1933, here in Duneland's Jackson Township.
The presumed bombing of United Airlines Flight 247 remains unsolved—a case marked more by theory, conjecture and anecdote than hard evidence.
A flight falls near Jackson Center
A local-history presentation later gathered what little could be firmly established about the night Flight 247 fell from the sky. The aircraft, carrying four passengers and three crew members, crashed in what was then called Jackson Center, a wooded part of Jackson Township.
The transcontinental flight was bound for San Francisco and had nearly completed its Cleveland-to-Chicago leg. It had just radioed Chicago Municipal Airport when an explosion occurred near the tail. Two passengers seated at the rear fell from the aircraft. The other five people aboard—including the first flight attendant to die in a commercial air crash—remained with the Boeing as it went down.
The catastrophe made national headlines. Commercial aviation was still young, and transcontinental flights were unusual and expensive. It was equally momentous in Duneland.
A crowded and unprotected crash site
Crowds descended on the wreckage to look and collect souvenirs. One recollection recorded in 1999 described a responding firefighter taking a propeller from the scene with help from others and bringing it back to town, where it remained displayed for years.
Because the propeller could not be found, investigators initially considered propeller failure as a possible cause. Other potential evidence almost certainly disappeared as well.
Local residents remembered wreckage and personal effects displayed in a hardware-store window. Children and adults alike carried away small pieces of aluminum. The scene was not sealed in the way a modern crash site would be.
Authorities also did not reconstruct the aircraft. While its remains were still on the ground, the Boeing was sold for scrap and hauled away. Pieces may have survived for decades in trunks, drawers, attics, garages and barns throughout the area.
The investigation reaches a dead end
Melvin Purvis, then head of the federal investigative agency's Chicago office, was dispatched to the scene. He would later become known for pursuing several high-profile Depression-era criminals.
Agents consulted laboratories at the University of Chicago and Northwestern University. Tests identified traces of nitroglycerin and other chemicals associated with an explosion on pieces of wreckage, but the investigation advanced no further.
Several explanations circulated. One theory connected the bombing to labor conflict involving the airline. Another suggested that organized crime wanted to kill a judge believed to use the flight regularly. The judge was not aboard that night, and federal investigators rejected the latter theory. No conclusive support emerged for either claim.
One account offered an especially intriguing detail: witnesses may have seen a man board in Cleveland with a suitcase, change his mind and leave the aircraft. No one could recall whether he took the suitcase with him.
A mystery shaped by lost evidence
What survives is an anecdotal record assembled from official findings, community recollections and later historical discussion. The carnival atmosphere at the wreckage and the casual handling of physical evidence resemble accounts of 19th-century transportation disasters more than a modern aviation investigation.
The confirmed traces of explosive material established the likelihood of sabotage. The missing evidence, early disposal of the aircraft and absence of a proven suspect ensured that the central question—who brought down Flight 247, and why—remained unanswered.