A United DC-6 at Stapleton Airport
|Date||November 1, 1955|
|Aircraft type||Douglas DC-6B|
|Aircraft name||Mainliner Denver|
|Flight origin||LaGuardia Airport, New York, New York|
|1st stopover||Chicago Midway International Airport, Chicago, Illinois|
|2nd stopover||Stapleton International Airport, Denver, Colorado|
|3rd stopover||Portland International Airport, Portland, Oregon|
|Destination||Seattle-Tacoma International Airport, Seattle, Washington|
United Airlines Flight 629, registration N37559, was a Douglas DC-6B aircraft, named "Mainliner Denver," which was blown up with a dynamite bomb placed in the checked luggage on November 1, 1955. The explosion occurred over Longmont, Colorado, while the airplane was en route from Denver, Colorado, to Portland, Oregon, and Seattle, Washington. All 39 passengers and five crew members on board were killed in the explosion and crash.
Investigators determined that Jack Gilbert Graham was responsible for bombing the airplane to kill his mother and obtain a large life insurance policy on her. Graham, who already had an extensive criminal record, was tried, convicted and executed for his crime.
Flight and explosion
The flight had originated at New York City's La Guardia Airport and made a scheduled stop in Chicago before continuing on to Denver's Stapleton Airfield. At Denver, there was a crew change; and Lee Hall, the Captain who assumed command of the flight for the segments to Portland and Seattle, was a World War II veteran.
The flight took off at 6:52 p.m. Mountain time. Eleven minutes later, Stapleton Airport tower controllers saw two bright lights suddenly appear in the sky north-northwest of the airport. Both lights were observed for 30–45 seconds, and both fell to the ground at roughly the same speed. The Controllers then saw a very bright flash originating at or near the ground, intense enough to illuminate the base of the clouds above the source of the flash. Upon observing the mysterious lights, the Controllers quickly tried to determine if they were indications of an aircraft in distress and contacted all aircraft flying in the area; all flights were quickly accounted for except for United Flight 629.
Numerous telephone calls soon began coming in from farmers and other residents near the town of Longmont, who reported loud explosions and fiery debris falling from the nighttime sky—the remains of Flight 629. Ground searchers who reached the crash site noted that all 44 people aboard the DC-6B had died instantly. The debris from the accident was scattered across 6 square miles of Weld County, Colorado.
There was early speculation that something other than a mechanical problem or pilot error was responsible. The November 2 edition of The New York Times reported a witness to the tragedy describing what he heard: "Conrad Hopp, a farmer who lives near the crash scene, said he and members of his family 'heard a big explosion — it sounded like a big bomb went off and I ran out and I saw a big fire right over the cattle corral. I hollered back to my wife that she'd better call the Fire Department and ambulance because a plane was going to crash. Then I turned around and it blew up in the air.'"
FBI investigators led by J. Edgar Hoover and Special Agent John McCulloch determined that the aircraft began to disintegrate near the empennage, or tail, and that the aft fuselage had been shattered by a force strong enough to cause extreme fragmentation of that part of the aircraft. The explosion had been so intense that investigators thought it unlikely to have been caused by any aircraft system or component. There was also a strong smell of explosives on items from the No. 4 Baggage Compartment.
Suspicions that a bomb had been placed in luggage loaded aboard the aircraft were fueled by the discovery of four pieces of an unusual grade of sheet metal, each covered in a gray soot. Further testing of the luggage from No. 4 Compartment showed that each piece was contaminated with chemicals known to be byproducts of a dynamite explosion.
The FBI, certain that the aircraft had been brought down by a bomb, performed background checks on the passengers. Many had purchased life insurance at the airport just before boarding. One such insuree was Daisie Eldora King, 53, a Denver businesswoman who was en route to Alaska to visit her daughter. When agents identified her handbag, they found a number of newspaper clippings containing information about King's son, John Gilbert Graham, who had been arrested on a Forgery charge in Denver in 1951. Graham, who held a grudge against his mother as the result of an unhappy childhood, was the beneficiary of both her life insurance policies and her will. Agents also discovered that one of Mrs. King's restaurants, the Crown-A Drive-In in Denver, had been badly damaged in an explosion; Graham had insured the restaurant and then collected on the property insurance following the mysterious blast.
Agents subsequently searched Graham's house and automobile and found wire and other bomb-making parts identical to those found in the wreckage. They also found an additional $40,000 in life insurance policies; however, Mrs. King had not signed either these policies or those purchased at the airport; and they were, therefore, worthless. Graham told Agents that his mother had packed her own suitcase; but his wife, Gloria, revealed that Graham had wrapped a "Christmas present" for his mother on the morning of the day of Mrs. King's ill-fated flight.
Faced with the mounting evidence and discrepancies in his story, on November 13, 1955, Graham finally confessed to having placed the bomb in his mother's suitcase, telling the police:
- "I then wrapped about three or four feet of binding cord around the sack of dynamite to hold the dynamite sticks in place around the caps. The purpose of the two caps was in case one of the caps failed to function and ignite the dynamite ... I placed the suitcase in the trunk of my car with another smaller suitcase...which my mother had packed to take with her on the trip."
Authorities were shocked to discover that there was no Federal statute on the books at the time (1955) that made it a crime to blow up an airplane. Therefore, on the day after Graham's confession, the Colorado District Attorney moved swiftly to prosecute Graham via the simplest possible route: Premeditated Murder committed against a single victim—his mother, Mrs. King. Thus, despite the number of victims killed on Flight 629 along with Mrs. King, Graham was charged with only one count of first degree murder. It was the first trial in Colorado to be televised, and it was covered by KLZ (now KMGH-TV) & KBTV (now KUSA-TV).
As the case progressed, Graham quickly recanted his confession; but, at his 1956 trial, his defense was unable to counter the massive amount of evidence presented by the prosecution. He was convicted of the murder of his mother and, after a few short delays, was executed in the Colorado State Penitentiary gas chamber on January 11, 1957. Before his execution, he said about the bombing, "as far as feeling remorse for these people, I don't. I can't help it. Everybody pays their way and takes their chances. That's just the way it goes."
United still uses the flight number 629 today on its Washington (National) - Chicago (O'Hare) route.
The bombing of United Flight 629 was also featured in an hour-long episode of the television series "A Crime To Remember" on original airdate December 3, 2013.
Flight 629 was the second known case of an airliner being destroyed by a bomb over the mainland United States. The first proven case of sabotage in the history of commercial aviation occurred on October 10, 1933 near Chesterton, Indiana, when the empennage (tail) was blasted from a United Air Lines Boeing 247 by a nitroglycerin bomb set off with a timing device. The three crew members and four passengers were killed in the crash. No suspect was ever brought to trial in the case.
Other crashes in the United States caused by bombs include:
- National Airlines Flight 967 over the Gulf of Mexico on November 16, 1959, killing 42.
- National Airlines Flight 2511 over North Carolina on January 6, 1960, killing 34.
- Continental Airlines Flight 11 over Unionville, Missouri on May 22, 1962, killing 45.
- Criminal Occurrence description. Retrieved 5 December 2013.
- Field, Andrew J. (2005). Mainliner Denver: The Bombing of Flight 629 (Google books limited preview). Boulder, Colorado: Johnson Books. ISBN 1-55566-363-X [Amazon-US | Amazon-UK].
- Gero, David (1997). Flights of Terror: Aerial Hijack and Sabotage Since 1930. Haynes Publishing. ISBN 1-85260-512-X [Amazon-US | Amazon-UK].
- LIFE Magazine, Vol. 39, No. 22, November 28, 1955 "A Case of 44 Midair Murders
- Sabotage: The Downing of Flight 629
- FBI History - Famous Cases: Jack Gilbert Graham
- Civil Aeronautics Board Aircraft Accident Report on Flight 629 from the Department of Transportation Special Collections