In episode 91 of Take to the Sky: the Air Disaster Podcast, we explore United Flight 629, which was blown out of the sky at 11,000 feet altitude by an onboard bomb planted in a passenger’s suitcase shortly after takeoff. The explosion tore apart the plane and killed all 39 passengers and 5 crew members. The FBI discovered the suitcase containing the bomb belonged to passenger Daisie Walker King, which led to the identification that her son, Jon Gilbert Graham, intentionally planted the bomb so his mother would die in the onboard explosion. The Colorado State Attorney General tried Graham for the murder of his mother, and in 1957, Graham was put to death for his crime. The fate of United 629 is significant because after the bombing, a law was passed that made it illegal to intentional bomb a commercial aircraft. The disaster also paved the way for subsequent FBI bombing investigations. 

United Airlines Flight 629 Takes Off from Denver for Portland with 44 People Onboard

Back in 1955, the year in which our story takes places, flying commercial was still a privilege for the few passengers that could afford to do so. And if you were able to buy a plane ticket, you were probably flying because you needed to get somewhere for important reasons, not just for a leisurely vacation. And this was true for most of the 39 passengers who booked a ticket on November 1st for United 629. We also talked about this was the time during the Golden Age of Flying in episode 7, the 1956 Grand Canyon Midair Collision. People got dressed up for a flight. It was a big deal. 

United Flight 629, a Douglas DC-6B aircraft known as the “Mainliner Denver”, was a regularly scheduled route between New York and Seattle, with plenty of stops along the way, including the Denver to Portland leg, where our story begins.

Waiting to board the evening flight west at the Stapleton Airport in Denver, Colorado, is passenger Helen Fitzpatrick, who is flying with her baby son James Jr. It is a special flight for Helen and baby James as Helen’s husband James Sr. had been stationed overseas in Okinawa since the day right after baby James was born – and he hadn’t seen his wife or son since then. Now 14-month-old James would be reunited with his father as Helen planned to fly this route all the way to Seattle, and then from there, make her way to Japan and reunite their family. 

Charles and Elizabeth Edwards were taking the opportunity to get two visits out of their trip. First, they planned to visit Elizabeth’s sister in Seattle and then they would plan a stop at Pearl Harbor in Hawaii, where their son was stationed. 

Louise Bunch considered herself "lucky" to get a last-minute reservation. Two eleventh-hour changes in plans put her aboard Flight 629. When the airport confirmed her last-minute Portland booking, she happily canceled her overnight reservation at a Colorado Springs hotel and made her way to the airport, much relieved. 

And then there was Daisie Walker King, a successful Denver businesswoman, who was headed all the way to Alaska to visit her daughter and perhaps to get in some time hunting.

While these and many other passengers awaited takeoff, the Denver crew assigned to the flight was already at the airport and completing their pre-flight tasks. The flight would be commanded by Captain Lee H. Hall and co-piloted by First Officer Donald A. White. 

A flight engineer rounded out the flight crew, and today that post would be filled by Flight Engineer Samuel F. Arthur. They would be joined by two experienced United stewardesses (as they were called then), Peggy Peddicord and Jacqueline Hinds, who would work diligently to make the 39 passengers feel at home on the flight.

Soon after the flight crew completes their pre-flight preparations, the plane is refueled, and all the passenger luggage is loaded into the plane’s cargo hold. And with that, United 629 is ready for takeoff.

United Airlines Flight 629 Fails to Respond to Controllers Shortly After Takeoff

Captain Hall taxied the plane to the assigned runway, and then at 6:52 pm, the plane lifted off and was cleared to climb all the way to its assigned cruising altitude of 21,000 feet (or 6400 meters). But, sadly, United 629 never reaches that altitude.

Seven minutes after Flight 629 took off, Stapleton air traffic controllers saw two bright lights suddenly appear in the sky. The lights were observed for 30–45 seconds, and both fell to the ground at roughly the same speed. Then the controllers witnessed a very bright flash near the ground, which was so intense it illuminated the base of the clouds 10,000 feet above. Panicked, controllers frantically contacted all aircraft flying in the area. All flights were quickly accounted for, except for United Flight 629.

United Airlines Flight 629 Explodes in the Sky, Debris Rains Down on town of Longmont, CO

Back on the ground, 18-year-old Conrad Hopp is sitting down to dinner with his family on a farm east of Longmont, Colorado, which is just outside Denver. Like so many times before, the Hopp family had spent all day in the fields, harvesting sugar beets.

And then, as they sat down for their well-earned dinner, something happened that would forever change their family. The Hopps heard a very loud explosion that shook all the windows in the house. Startled, they looked outside and saw a ball of fire careening through the sky. And that’s not all. They could also hear the unmistakable roar of a plane’s engines.

Conrad and his brother rushed outside, trying to keep their gazes focused on the fire ball, but they lose sight of it as it disappeared behind some outbuildings on the edge of their farm. They hastily jumped into Conrad’s ’54 Chevy and drive in the direction of the fire ball until they reached an irrigation ditch and a thicket of trees. Here, Conrad parked the car, and his headlights illuminated something awful: it was the back of an airline seat.

His brother climbed over a fence and ran around to the front of the airline seat. There he made a horrific discovery: it was not just an airline seat; a body was still strapped in by the seatbelt. 

It was a chilly night, and Conrad’s brother reflexively yelled for him to go and grab some coats, thinking these folks would probably need to keep warm. But the brothers would soon find out, coats would do nothing to help these fallen passengers. 

The Hopp family is not the only family to have seen the fireball in the sky that night. In the moments after the fire ignited in air, hundreds of callers flooded the Longmont Police Department, and thousands began to flock to the area.

Keith Cunningham, the Longmont police chief at the time, called the Colorado State Patrol and sent every police officer and firefighter in the city to the scene, and dispatched every ambulance. A few minutes later, a patrolman radioed back with the grimmest of all news: the ambulances would not be necessary.

Rescue personnel soon confirmed the plane that had exploded and fallen to the earth was United 629. All 44 people onboard, including the three flight crew members, two flight attendants, and 39 passengers, have perished. This disaster came on the heels of three other United Airlines disasters in the decade prior: just a month earlier, 66 people died when another United plane smashed into a mountain in Medicine Bow Peak, Wyoming, and then two other United planes had been lost earlier in the decade along the same route. Remember, though this was the Golden Age of Flying, there were many things not yet figured out in aviation safety. 

United 629 Debris Reveals Presence of Onboard Bomb in Passenger Baggage Compartment

Soon, many residents who flocked to the area after seeing the fire ball in the sky now understand the gravity of the situation: a passenger plane has exploded in the sky and fallen back to earth in pieces, bringing with it seats, clothing, luggage, and human bodies. Though much of the debris was centered in an area near Longmont, the entire debris field stretched out over a 15-mile (or 24-kilometer) range. Hundreds of searchers and volunteer residents formed a line, standing about an arm's length apart, and walked across the vast alfalfa and sugar beet crops, combing the ground for every piece of the wreckage.

Many people immediately suspected foul play in the downing of Flight 629. The very first night the plane exploded, rescuers noticed the distinct odor of dynamite throughout the wreckage and pointed out that some of the bigger pieces of the plane appeared to have dropped directly from the sky and sunk deep into the earth. Despite these clues, within a day of the crash, a United executive told reporters, "Sabotage is not considered.” This statement would end up being a terribly wrong. 

Investigators from a range of agencies including the Civil Aeronautics Board (as this was before the NTSB was an agency), FBI, FAA, Civil Air Patrol, United States Postal Service (yes, because Flight 629 was carrying US mail bound for Alaska), and United Airlines combed the wreckage. The wreckage was taken to a warehouse at the Stapleton airport, where investigators began to reconstruct the body of the plane around a frame of chicken wire, piecing together hundreds of scraps of the disintegrated aircraft.

Within hours of the crash, it had become clear that an explosion of "such great intensity" wasn't a malfunction of the plane, the Civil Aeronautics Board wrote in its report. Six days after the downing of the plane, the Board determined that United 629 had climbed to about 11,000 feet (or 3,352 meters) when the explosion happened. 

The plane first began to disintegrate near the tail section, and the aft (or rear) fuselage had been shattered by the force of the explosion, which immediately caused extreme fragmentation of the rear portion of the aircraft. The explosion had been so intense that investigators thought it unlikely to have been caused by any aircraft system or component. And soon investigators themselves discover what so many searchers and rescuers had already noticed: there was a strong smell of explosives on items specifically coming from the number 4 baggage compartment (which was at the back of the aircraft). 

Determining that a bomb was the most likely cause of the inflight explosion, the Board hands off the investigation to the FBI, which now takes full control as it shifts from an accident investigation to a criminal one. 

FBI Confirm Passenger was Target of Onboard Bomb

Before rushing to any conclusions, the FBI needed to test and confirm a bomb had indeed been placed in the baggage compartment aboard the aircraft. They find four pieces of an unusual grade of sheet metal, each covered in a gray soot. Further testing of the cargo pit showed that each piece was contaminated with chemicals known to be byproducts of a dynamite explosion. 

Confirming that a bomb caused the explosion that brought down United Airlines Flight 629, investigators comb through all the debris, focusing now on passenger luggage to see if they could tell in which suitcase the bomb had been placed. Knowing that information would help point them in the direction of either a perpetrator or a target. And the luggage is where they get their break: every known suitcase on the flight was recovered, most in remarkably good condition showing no signs of a bomb exploding within them—except the one belonging to passenger Daisie Walker King. We had mentioned her at the start of our story and noted that Daisie was a successful Denver businesswoman who was headed to Alaska to visit her daughter. 

Investigators begin to dig into Daisie’s life, not knowing whether she was the bomber or had been the target of the bomb. Upon further investigation, authorities found that Daisie's son John Graham had been convicted of several crimes, including stealing blank checks from an employer and running bootleg liquor. FBI Director J. Edgar Hoover ordered agents to "focus on him" after learning this information. 

FBI Focuses on Passenger’s Son as Key Suspect in United 629 Bombing 

Digging even deeper into the dynamic that existed between Daisie and her son John, investigators hear from neighbors that the mother and son had a very tense relationship, with neighbors frequently hearing quarrels between the two. And most troubling, investigators uncover a lifetime of resentment between the two. 

Born during the Great Depression, John was Daisie's second child, from a second husband. Her first marriage, which produced a daughter, had ended in divorce. Husband number two had died of pneumonia in 1937, and poverty forced Daisie to leave John in an orphanage. She remarried in 1941, but she did not take custody of John again until 1954, the year her third husband, Earl King, died, leaving her comfortably well off. Many people said this was the primary reason John resented his mother – she had chosen not to come get him from the orphanage even though she could have. 

Over the years, John had constantly been in scraps with the law — for forgery, illegal gun possession, and hauling liquor into dry states — but appeared to be trying to pull his life together. Daisie paid off his fines and set him up in a business, a drive-in restaurant. In September 1955, less than two months before the bombing, a gas explosion damaged John’s restaurant. Police suspected that the blast was arson but could not prove it. 

For that event, John collected a $1,200 insurance claim (worth about $12,500 today). John had even tried to collect more insurance after he drove his car onto a railroad track, leaping out seconds before the impact. 

When the FBI searched John’s home, they found copper wire, the kind used in detonating primer caps, and several life insurance policies John had purchased on his mother at the Stapleton airport the day of the flight. (In mid-century America, life insurance vending machines, where a policy could be purchased for as little as 25 cents, were common features at airports of all sizes.) Considering Jack’s insurance claim would have paid a maximum of $37,500, John essentially placed a price on the lives of his 44 victims at less than $1,000 each.

The FBI brought John in for questioning, and soon his tone shifted toward a confession when he asked them, "OK, where do you want me to start?" In great detail, he described building and planting the bomb that killed his mother and 43 others on United Airlines Flight 629.

John Graham Receives Death Penalty for Downing United Flight 629

It had been a simple device, constructed of 25 sticks of dynamite, a six-volt battery, two electric primer caps — in case one failed — and a timer set to detonate in about 90 minutes. He then took the sack of dynamite, with the battery and timer attached, and placed it in Daisie’s large suitcase. He had told his mother inside her suitcase was a present he had bought for her, a way to explain why her bag was now so heavy. John then drove his mother to the airport, careful to help her with her unusually heavy bag at the ticketing desk. And then he watched her board Flight 629.

But what was unconscionable about John’s actions to investigators and mental health professionals alike, was even if he hated his mother, how could he not care about the other 43 innocent people on the plane, who had nothing to do with his grudge against his mother Daisie?

When he spoke with psychiatrists later, John admitted that he realized there would be dozens of other people on the plane. Chillingly, he told the doctors, "But the number of people to be killed made no difference to me. It could have been a thousand. When their time comes, there is nothing they can do about it."

At the time, the maximum federal penalty for sabotaging an aircraft during peacetime was just 10 years in prison. So, the case was turned over to the state, which could prosecute John for murdering his mother, and sentence him to death in the gas chamber.

John did not testify at his trial in April 1956, which was also the first-time television cameras were allowed in court. John later recanted his initial confession, but at his trial the five-page written confession, initialed by him on each page and signed on the last, was read in court.

It took just 72 minutes for the jury to find him guilty and he was sentenced to die. Shortly before the execution, John said, "Everybody pays their way and takes their chances. That's just the way it goes." John Graham was executed on Jan. 11, 1957, having shown zero remorse for his crimes. 

As a result of the aircraft explosion, and because there was no law against bombing an aircraft, a bill was introduced and signed by President Dwight D. Eisenhower on July 14, 1956, which made the intentional bombing of a commercial airline illegal. And as for FBI investigations, the downing of United 629 was the FBI’s first investigation of a major criminal attack on a U.S. airline. The process used to identify what happened and who committed the act became the new investigative process used for decades to come. 

The Downing of United Airlines Flight 629 Continues to Haunt Residents of Longmont, CO 

Journalist Robert Garrison of the Denver Channel visited the Hopp family in the years after the explosion. What comes next is based on his article and interviews with the family. 

The Hopp family continues to harvest their fields. But every now and then, they find a bare spot in the crop. It is always where a body fell into the ground, and the alfalfa just didn’t grow back.

Through the years, the family would find small items buried in the dirt; pens and eyeglasses, small personal effects that fell with the bodies. When one of their cows died shortly after the explosion, they found a hunk of metal lodged inside of it.

Conrad Hopp’s father wasn't a superstitious man, but after the explosion, the longtime farmer refused to water the fields at night on the east side of the farm, where the wreckage landed. It just made him feel too uneasy when he was out there. Hopp's brothers would even say they heard ghosts. Conrad, himself, tries not to think about the explosion too often – if he doesn't have to.

Today, the rolling farmlands look about the same as they did in 1955, and Conrad Hopp can picture where everything happened. He can spot the two trees near where the tail of the plane landed. And he can still see where he and his brother took off across the farm toward the wreckage, where he saw that first body strapped in the airplane seat.

Conrad predicts that one day, some of the farmland beyond their farm, where debris from the plane also fell, may become part of a subdivision. If it does, he wonders if the people in those new homes will ever find out what their homes are built upon, what came before them. He wonders if they will know that United 629 ever happened at all. 

And THAT is the heartbreaking story of the bombing of United Airlines Flight 629.