United Air Lines Flight 629 was a scheduled passenger flight from Denver, Colorado, to New York City when it tragically exploded in mid-air near Longmont, Colorado. The Douglas DC-6B airliner had just departed Denver International Airport filled with 39 passengers and five crew members. Shortly after takeoff, an explosion ripped through the aircraft, resulting in its rapid descent into the ground. The wreckage was scattered across the countryside, with witnesses reporting seeing flames and debris falling from the sky.

Investigators quickly set to work to determine the cause of the explosion. The subsequent investigation revealed that a suitcase containing a bomb had been placed on board the flight. This suitcase belonged to a passenger, a man named Edward D. Sweeney, who had a troubled history and was suspected of criminal activity. The motive behind the bombing was believed to be linked to a life insurance policy taken out in favor of his own family.

The aftermath of the bombing led to increased scrutiny of aviation security protocols and highlighted the potential dangers of unchecked baggage. Moreover, the tragedy raised awareness and prompted discussions surrounding safety measures in air travel, leading to significant changes in regulations regarding airline security.