The Tragic 1955 Plane Crash Over Longmont That Changed Aviation Forever

On November 1, 1955, a routine flight from Denver’s Stapleton Airport turned into one of the darkest moments in Colorado’s history. United Airlines Flight 629, a DC-6B aircraft, exploded midair just minutes after takeoff, scattering debris over the sugar beet fields near Longmont.

The tragic plane crash marked the first confirmed act of airline terrorism in the United States. All 44 passengers and crew perished in what would become a pivotal case in aviation security and criminal investigations.

The impact of Flight 629 extended far beyond the crash site, influencing airport security protocols and criminal law both in Colorado and nationwide.

What Happened to United Airlines Flight 629?

On the evening of November 1, 1955, families in Longmont, Colorado were settling in after a typical autumn day. Farmers had spent hours harvesting sugar beets in their fields north of town, near Highway 66 in Weld County.

Air traffic controllers at Stapleton Airport quickly realized something was wrong when Flight 629 stopped responding. Shortly after takeoff, the aircraft had vanished from radar.

Just after 7 p.m., a thunderous explosion shook the sky. Witnesses reported seeing a fireball streak across the night, followed by debris falling across the farmland. 

Conrad Hopp, a local farmer, ran toward the wreckage with his brother, only to find the twisted remains of an airline seat—still strapped with a passenger.

Within minutes, first responders and bystanders flooded the crash site, only to realize there were no survivors.

The wreckage was scattered across six square miles, with parts of the plane buried deep in the fields. 

Though the community was in shock, volunteers and authorities worked through the night cleaning up the household items, luggage, and personal belongings that littered the crash site.

Investigation of the Crash

In the hours following the United Airlines Flight 629 disaster, investigators quickly realized something was off about the plane crash. The wreckage pattern told a chilling story—pieces of the aircraft were scattered in a way that suggested an in-flight explosion rather than mechanical failure.

Forensic experts noted:

• Burn marks and blast damage inconsistent with an engine failure.
• The strong smell of dynamite lingering in the debris.
• A concentrated impact zone near the rear cargo hold.

These findings pointed to a deliberate act, and within days, the case was turned over to the FBI.

The FBI’s Breakthrough

Investigators combed through passenger belongings, looking for anomalies. One suitcase stood out—it belonged to Daisie King, a 54-year-old woman from Denver. Unlike other luggage, hers was obliterated, with traces of chemical residue later identified as explosive material.

Suspicion quickly fell on John Gilbert Graham, her son. Authorities uncovered several life insurance policies taken out in his mother’s name, purchased just hours before the flight. His nervous behavior during questioning raised further red flags.

Graham’s Arrest and Confession

With mounting evidence, the FBI confronted Graham. Under pressure, he confessed—he had hidden a homemade dynamite bomb in his mother’s luggage, intending to collect insurance money. He showed no remorse for the 43 other lives lost.

The Historic Trial of John Graham

America’s First Televised Trial

The trial of John Gilbert Graham was groundbreaking—it was the first trial in U.S. history to be televised. Cameras rolled as prosecutors laid out their case, capturing every moment of the sensational courtroom drama.

Key moments included:

• Eyewitness testimonies from investigators and airport staff.
• Forensic evidence linking Graham’s homemade bomb to his mother’s luggage.
• The life insurance policy purchases just before the flight.

The jury took just 69 minutes to reach a verdict—guilty of first-degree murder. The court sentenced Graham to death, making him one of the most infamous criminals in Colorado history.

Execution of John Gilbert Graham

Even on death row, Graham showed no remorse. He spent his final months at Colorado State Penitentiary, refusing to discuss his crimes with clergy or reporters.

On January 11, 1957, he was led to the gas chamber, where he uttered a final “thank you” before his execution. His case set a precedent for airline security, criminal investigations, and the use of television in courtrooms.

The Tragedy’s Lasting Impact on Aviation and Security

New Airline Security Measures

The bombing of Flight 629 exposed a terrifying vulnerability—passengers could check in unsearched luggage with deadly consequences. At the time, there were no formal baggage screening procedures.

Following this tragedy, the U.S. government and airlines began implementing:

• Stricter baggage checks to prevent explosives from being smuggled onto flights.
• Better tracking of passenger belongings to identify potential threats.
• Tighter regulations on life insurance policies purchased at airports to prevent fraud-motivated attacks.

These changes laid the foundation for modern aviation security, setting the stage for stricter measures in later decades, including the formation of the TSA after 9/11.

How Flight 629 Changed Colorado’s History

For the Longmont community, the scars of November 1, 1955, remain. Locals who rushed to the scene that night never forgot the horrific sight of burning wreckage and personal belongings scattered across farmland.

Yet, for decades, the tragedy was largely forgotten outside of Colorado. No memorial was ever constructed, despite the public attention the disaster received at the time. With memorial efforts now underway, there is renewed recognition of the lives lost and the historical significance of the event. 

Why Was There Never a Memorial For Flight 629?

Despite being one of Colorado’s worst mass murders, the Flight 629 disaster was largely forgotten for decades. Unlike other major tragedies, it did not receive a permanent memorial or widespread recognition.

Several factors contributed to this:

• Public memory was focused on World War II and the Korean War, both of which overshadowed domestic tragedies.
• Airline bombings were rare, and security measures quickly changed, leading many to move on.
• The victims’ families, spread across the country, had no central place to mourn.

For years, only local historians and aviation experts kept the story alive, but efforts to honor the victims have gained momentum in recent years.

The Efforts to Build a Memorial

The Flight 629 Memorial Committee is working to establish a permanent tribute in Weld County, near the crash site. The proposed memorial will:

• List the names of all 44 victims.
• Honor the first responders and citizens who helped that night.
• Serve as an educational site to preserve the history of Flight 629.

How to Contribute

You can help ensure that Flight 629’s victims are never forgotten by supporting the memorial fund. Donations will go toward:

• Constructing the monument.
• Hosting annual remembrance ceremonies.
• Educational efforts to preserve the story.

Frequently Asked Questions (FAQ)

What caused the explosion of United Airlines Flight 629?

The crash was caused by a bomb hidden in a passenger’s luggage. The explosive device, made with 25 sticks of dynamite, was placed in Daisie King’s suitcase by her own son. It detonated 11 minutes after takeoff, causing the aircraft to break apart midair.

Who was responsible for the bombing?

John Gilbert Graham, King’s son, orchestrated the bombing to collect on multiple life insurance policies he had taken out on his mother. He showed no remorse for the 43 other lives lost.

How did investigators solve the case?

The FBI examined the wreckage, noticing blast patterns consistent with an intentional explosion. They identified King’s luggage as the source, leading them to Graham, whose suspicious behavior and financial motives quickly unraveled.

Why wasn’t there a memorial built sooner?

Public focus remained on World War II and the Korean War, overshadowing domestic tragedies. Additionally, victims’ families were scattered, and the event slowly faded from public memory—until recent efforts to honor those lost gained traction.