Sabotage: The Downing of Flight 629
"Out of the Ordinary"
After the Civil Aeronautics Board (CAB) technicians examined the wreckage, it became very clear that the cause of the explosion did not originate with the aircraft itself. Patterson issued a statement from the United. home office that the explosion "was completely foreign to the aircraft or to airline operations." By November 5, the CAB formally requested the FBI to conduct a criminal investigation into the matter. Chief investigator James Reyton told reporters that the luggage in the airliner had a smell "like gunpowder or an exploding firecracker."
In the meantime, the U.S. Postal Service was assigned to retrieve any mail from Flight 629 found on the ground. Over a period of several days, postal authorities recovered over 400 pounds of mail that was spread out over an area eight and a half miles long and four miles wide. The pattern of the recovered mail added to the belief that an explosion had occurred on board. One official told the Denver Post, "There's not one thing outstanding, but things appear out of the ordinary." When pressed for an explanation, he replied, "We are investigating the possibility of sabotage."
Slowly, methodically, search teams collected every scrap of metal and debris they could find. Each location of every piece was recorded and mapped on a huge board at a staging hangar in Stapleton airport. Like a giant jigsaw puzzle, investigators began to re-assemble the decimated aircraft. Engineers from Douglas Aircraft Corporation and the technicians from the CAB studied the serrated metal pieces from the underbelly of the plane. Soon it became obvious that the point of explosion was located in the rear luggage compartment of the DC-6B known as luggage pit #4. The recovered luggage from that area had a strong gunpowder odor and was mangled in a way different from the rest of the items, indicating some sort of explosion. Investigators then reviewed the cargo manifest of flight 629 which showed the type and sizes of all cargo on board. There was nothing of an explosive nature in the cargo bay or anything that could be made to explode. Furthermore, it was determined that all the cargo contained in bin #4 had been loaded on the aircraft in Denver.
As the search continued, engineers found four small pieces of an unusual grade of sheet metal. These pieces could not be matched to any part of the DC-6B. Additionally, each one of these fragments was heavily coated with a gray soot residue, which is normally associated with an explosion. Upon further testing, technicians determined that most of the debris from the cargo area, including the luggage, contained traces of sodium carbonate, nitrates and sulfates. The presence of these chemical compounds traditionally indicates the use of dynamite. The FBI became convinced that a bomb, consisting of a large quantity of dynamite and a timing device, had been placed on the aircraft at Stapleton just prior to takeoff.
But who would do such a thing? And why?