UI Douglas DC-6B N37559,

ASN Wikibase Occurrence # 334804

Date:	Tuesday 1 November 1955
Time:	19:03
Type:	Douglas DC-6B
Owner/operator:	United Airlines
Registration:	N37559
MSN:	43538/224
Year of manufacture:	1952
Total airframe hrs:	11949 hours
Engine model:	Pratt & Whitney R-2800-CB16
Fatalities:	Fatalities: 44 / Occupants: 44
Aircraft damage:	Destroyed, written off
Category:	UI
Location:	Longmont, CO - United States of America
Phase:	En route
Nature:	Passenger - Scheduled
Departure airport:	Denver-Stapleton International Airport, CO (DEN/KDEN)
Destination airport:	Portland International Airport, OR (PDX/KPDX)
Investigating agency:	CAB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
United Air Lines Flight 629 was a scheduled daily flight between New York-LaGuardia Field, New York, and Seattle, Washington. There were scheduled stops at Chicago, Illinois; Denver, Colorado; and Portland, Oregon, with crew changes at Chicago and Denver.
On November 1, 1955, this flight was routine to Denver where the flight landed at 18:11, 11 minutes late because of several brief ground delays. At Denver the aircraft was refueled to 3,400 gallons of fuel and was checked for the continued flight.
When the flight arrived at Denver, the rear cargo hold (No. 4), was emptied and thereafter loaded with mail, freight, and passenger luggage, all of which originated at Denver.
Flight 629 taxied to runway 8R and at 18:44 the flight was in runup position where it was given ATC clearance for the flight to Portland. Following takeoff the flight reported its "off time" to the company as 18:52 and thereafter reported passing the Denver VOR at 18:56. This communication was the last from the flight.
About 19:03 the Denver tower controllers saw two white lights, one brighter than the other, appear in the sky north-northwest of the airport and fall to the ground. It was soon determined that flight 629 had crashed.
Investigators determined that the tail section of the aircraft separated in mid-air following a violent explosion in the rear. The remaining aircraft then broke up.

On November 14, 1955, agents of the Federal Bureau of Investigation (FBI) took into custody John G. Graham, the son of one of the passengers. Thereafter, he was indicted for acts leading to the destruction of the aircraft by means of a bomb explosion.
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. He wrapped dynamite sticks as a Christmas present.

PROBABLE CAUSE: "The disintegrating force of a dynamite bomb explosion which occurred in the no. 4 baggage compartment."

Accident investigation: