United 629: The night a son blew up his mother’s flight over Colorado | HO!!

I. The Flash Over Longmont

On the evening of November 1, 1955, the Colorado sky was clear, cold, and deceptively calm. The sun had just slipped behind the Rockies, painting the horizon in violet and copper streaks.
At exactly 6:52 p.m., United Airlines Flight 629, a DC-6B named Mainliner Denver, lifted off from Stapleton International Airport, bound for Portland, Oregon, with 39 passengers and 5 crew members aboard.

Eleven minutes later, it ceased to exist.

A bright orange flash lit the night sky over Longmont, thirty miles north of Denver. Windows rattled for miles. Farmers heard a roar that rose, cracked, and vanished, leaving only the hiss of wind across frozen fields.

Conrad and Martha Hopp, finishing supper in their farmhouse, thought a fuel truck had exploded on the highway. They stepped outside — and saw the sky raining fire.

“There was a glow, like the whole heavens were burning,” Conrad would recall decades later. “You could hear it — like the air itself was screaming.”

They didn’t know it yet, but what they were witnessing was the deadliest mass murder in modern Colorado history — and the first successful bombing of a commercial airliner in the United States.

II. The Debris Field

When Conrad reached his truck, the ground trembled again — a deep, dull thud rolling across the fields. He and his brother drove toward the glow, headlights slicing through the smoke. Within minutes, they were driving over fragments of metal, upholstery, and paper raining down like confetti.

“The closer we got,” he said, “the more it felt like driving through hell.”

In the middle of the field, a fireball the size of a barn burned so hot that sugar beets nearby had turned to ash. Seats were scattered across frozen furrows, their occupants still strapped in. A child’s shoe. A passport. The smell of jet fuel and dynamite.

Conrad called out for survivors. There were none.

Six square miles of farmland became a graveyard. The tail section, astonishingly intact, had crashed in the Hopps’ own sugar-beet field. The rest of the aircraft was scattered in pieces so small investigators initially believed two planes had collided midair.

By midnight, emergency crews arrived from Boulder, Longmont, and Denver. They carried lanterns and nausea. The wreckage was still smoldering when FBI agents arrived before dawn.

It didn’t take them long to suspect this was no accident.

III. The Smell of Dynamite

Airplane crashes were not new in the 1950s — but explosions were.

Investigators found no evidence of mechanical failure, no lightning strikes, no midair collision. What they did find was a smell that clung to the wreckage and to the memories of everyone who inhaled it.

“You could smell it,” Conrad said. “That tang, like burning matches and sulphur. Dynamite. I knew it right away.”

In the cornfield debris, agents recovered fragments of wiring, a twisted timer, and a fragment of galvanized pipe. They traced it to a time bomb — crude but effective — hidden in a piece of luggage in the plane’s cargo hold.

The conclusion was inescapable:
Someone on that flight had been murdered by design.

IV. The Passenger List

Within 48 hours, FBI Director J. Edgar Hoover ordered a full investigation. Fifty agents descended on Denver, sorting through what little remained of the plane — and the lives it carried.

Among the dead was Daisy E. King, 53, a Denver widow flying to Portland to visit her daughter. She’d checked in a single piece of luggage: a small suitcase wrapped with a ribbon. Inside, unbeknownst to anyone, were 25 sticks of dynamite wired to a timer.

Investigators traced the suitcase back to her son, John Gilbert Graham, a 23-year-old mechanic from Denver.

V. The Man Behind the Smile

John Graham did not look like a killer. He was clean-cut, soft-spoken, with a shy smile that reporters would later describe as “boyish.” But inside that modest frame lived a calculating resentment decades in the making.

Born in 1932, John’s childhood was a catalog of abandonment. His father died when he was young; his mother, Daisy, placed him in an orphanage. She remarried and built a small restaurant empire in Denver, while her son grew up poor, angry, and convinced that she’d discarded him like trash.

By his early twenties, John had accumulated a criminal record — check fraud, petty theft, embezzlement. Yet Daisy, still trying to “help,” gave him a job at her restaurant, the Crown-A-Drive-In. They appeared reconciled. They weren’t.

Coworkers later said John’s hatred was an open secret. “He talked about her like she was an enemy,” one recalled. “Said she cared more about her money than her own son.”

That bitterness would find a fuse.

VI. The Life Insurance

When Daisy King booked her flight to Portland, John drove her to the airport. He smiled, hugged her, and handed over her suitcase.

What she didn’t know was that inside, beneath the clothes and toiletries, he had hidden a bomb made from 25 sticks of dynamite, a battery, a timer, and a detonator fashioned from a flashlight bulb.

Before she boarded, he also purchased three life insurance policies on her at the airport counter — totaling $37,500 — payable to himself. In 1955, that was the equivalent of nearly half a million dollars.

It was greed disguised as grief.

At 6:52 p.m., Daisy’s plane took off. Eleven minutes later, John was home, eating dinner with his wife when the radio announced a plane explosion over Longmont.

He said nothing.

VII. The Investigation

The FBI’s Denver field office became the command center of an unprecedented investigation. Agents combed junkyards for dynamite receipts, interviewed miners, hardware clerks, anyone who sold blasting caps.

They found their first break when they learned that Graham had once worked in a quarry — and had access to dynamite. The second came when they traced the life insurance purchase to him.

When agents visited his house, they found tools, wire, and a roll of tape identical to that used in the bomb. They also found a stack of insurance papers on his kitchen table.

When confronted, John Graham’s composure cracked.

He confessed in a flat monotone, as if describing someone else’s story.
“I put the dynamite in her suitcase,” he said. “I guess I lost my head.”

It was the coldest confession the FBI had ever heard.

VIII. The Televised Trial

By early 1956, the murder trial of John Gilbert Graham became a national sensation. It was the first televised court trial in Colorado history — and, in many ways, the first modern media spectacle of American crime.

Cameras rolled as the young defendant sat behind the defense table, expressionless, watching footage of his own mother’s funeral.

Prosecutors played recordings of his confession. They showed diagrams of the DC-6, the impact zones, the wreckage patterns. Viewers saw the photographs — seats torn apart, faces blurred beyond recognition — and heard the quiet voice of the man who had caused it.

“I don’t feel sorry for her,” Graham said in one interview. “My mother never loved me. Why should I love her?”

The courtroom gasped.

The jury took 69 minutes to convict him.

On January 11, 1957, John Gilbert Graham was executed in Colorado’s gas chamber at Canon City. He was 25 years old.

IX. The Couple Who Remembered

For Conrad and Martha Hopp, life went on — but never untouched.

They’d been the first civilians on the crash scene, the first to see the bodies, the first to smell the dynamite. For decades they refused to speak publicly about it.

When they finally did, in an interview nearly sixty years later, Conrad’s hands still trembled.

“You don’t realize what you’re seeing when you see it,” he said. “Not till later. It stays with you. The smell. The quiet. The way the snow fell after the fire went out.”

He looked across the field where it happened. Subdivisions now cover most of it. Driveways where debris once burned. Children ride bicycles over ground that still hides fragments of twisted metal.

“There’s no marker,” Martha said softly. “No sign. Just memories.”

X. The Forgotten Flight

Flight 629 should have changed everything. It was, after all, the first proven act of airplane sabotage in U.S. history. It exposed glaring security flaws — anyone could check a bag without inspection, anyone could buy life insurance on the spot.

Yet, astonishingly, little changed. There were no metal detectors, no luggage screenings, no systematic reforms. America wanted to believe it was an anomaly — a tragedy born of greed, not a warning of what was to come.

Only decades later, after a string of midair bombings in the 1970s and 1980s, would the story of John Graham resurface as a grim precedent — the moment when innocence left the skies.

XI. A Son’s Psychology

What drove John Graham was not insanity, psychiatrists concluded, but resentment sharpened into purpose.

He wasn’t impulsive. He planned every detail — from the insurance policies to the timer setting that ensured the plane would explode over open farmland, leaving no survivors but minimizing ground casualties.

He didn’t hate strangers. He simply didn’t care about them. They were collateral in his war against one woman.

“Matricide is the oldest betrayal,” wrote a Denver Post columnist during the trial. “But Graham made it modern — he mechanized it.”

His execution drew little sympathy. Yet even in death, he forced America to face an uncomfortable question: How could a society that idealized family produce a son who turned his mother’s love into a ledger entry?

XII. The Legacy

Today, the site of the crash lies beneath suburban sprawl — tidy lawns, cul-de-sacs, playgrounds. There are no plaques, no memorials. The coordinates exist only in FAA archives and the fading memories of survivors’ families.

But if you stand north of Longmont on a clear November night, you can still feel it — that vast emptiness between the stars and the earth, the echo of a single, blinding flash that once turned a Colorado sky into a crime scene.

It began with a son’s hunger for money and ended with 44 souls scattered across frozen fields.

The official reports call it United Airlines Flight 629.
Locals call it the Longmont Explosion.
History knows it as the night a son blew up his mother’s flight over Colorado.

And every year, when November comes and the fields frost over, some swear they can still smell it — not the dynamite, but the grief that never burned away.