On 21 January 1968, a B-52G Stratofortress, serial number 58-0188, with the callsign "HOBO 28" from the 380th Strategic Bomb Wing at Plattsburgh Air Force Base, New York was assigned the "Hard Head" mission over Thule and nearby Baffin Bay.
 The bomber crew consisted of five regular crew members, including Captain John Haug, the aircraft commander.
Also aboard were a substitute navigator (Captain Curtis R. Criss) and a mandatory third pilot (Major Alfred D'Mario).

Before take-off, D'Mario placed three cloth-covered foam cushions on top of a heating vent under the instructor navigator's seat in the aft section of the lower deck.
Shortly after take-off, another cushion was placed under the seat.
The flight was uneventful until the scheduled mid-air refueling from a KC-135 Stratotanker, which had to be conducted manually because of an error with the B-52G's autopilot.
About one hour after refueling, while the aircraft was circling above its designated area, Captain Haug directed co-pilot Svitenko to take his rest period.
His seat was taken by the spare pilot, D'Mario.
The crew was uncomfortable because of the cold, although the heater's rheostat was turned up, so D'Mario opened an engine bleed valve to draw additional hot air into the heater from the engine manifold.
Because of a heater malfunction, the air barely cooled as it traveled from the engine manifold to the cabin's heating ducts.
During the next half-hour, the cabin's temperature became uncomfortably hot, and the stowed cushions ignited.
After one crew member reported smelling burning rubber, they looked for a fire.
The navigator searched the lower compartment twice before discovering the fire behind a metal box.
He attempted to fight it with two fire extinguishers, but could not put it out.

At 15:22 EST, about six hours into the flight and 90 miles (140 km) south of Thule Air Base, Haug declared an emergency.
He told Thule air traffic control that he had a fire on board and requested permission to perform an emergency landing at the air base.
Within five minutes, the aircraft's fire extinguishers were depleted, electrical power was lost and smoke filled the cockpit to the point that the pilots could not read their instruments.
As the situation worsened, the captain realized he would not be able to land the aircraft and told the crew to prepare to abandon it.
They awaited word from D'Mario that they were over land, and when he confirmed that the aircraft was directly over the lights of Thule Air Base, the four crewmen ejected, followed shortly thereafter by Haug and D'Mario.
The co-pilot, Leonard Svitenko, who had given up his ejection seat when the spare pilot took over from him, sustained fatal head injuries when he attempted to bail out through one of the lower hatches.

The pilotless aircraft initially continued north, then turned left through 180° and crashed onto sea ice in North Star Bay at a relatively shallow angle of 20 degrees—about 7.5 miles (12.1 km) west of Thule Air Base—at 15:39 EST.
The conventional high explosive (HE) components of four 1.1 megaton B28FI thermonuclear bombs detonated on impact, spreading radioactive material over a large area in a manner similar to a dirty bomb. "
Weak links" in the weapon design ensured that a nuclear explosion was not triggered.
The extreme heat generated by the burning of 225,000 pounds (102 t) of jet fuel during the five to six hours after the crash melted the ice sheet, causing wreckage and munitions to sink to the ocean floor.

Haug and D'Mario parachuted onto the grounds of the air base and made contact with the base commander within ten minutes of each other.
They informed him that at least six crew ejected successfully and the aircraft was carrying four nuclear weapons.
Off-duty staff were mustered to conduct search and rescue operations for the remaining crew members.
Owing to the extreme weather conditions, Arctic darkness, and unnavigable ice, the base relied largely on the Thule representative of the Royal Greenland Trade Department, Ministry of Greenland, Jens Zinglersen, to raise and mount the search
On 21 January 1968, a B-52G Stratofortress, serial number 58-0188, with the callsign "HOBO 28" from the 380th Strategic Bomb Wing at Plattsburgh Air Force Base, New York was assigned the "Hard Head" mission over Thule and nearby Baffin Bay.  The bomber crew consisted of five regular crew members, including Captain John Haug, the aircraft commander. Also aboard were a substitute navigator (Captain Curtis R. Criss) and a mandatory third pilot (Major Alfred D'Mario).
Before take-off, D'Mario placed three cloth-covered foam cushions on top of a heating vent under the instructor navigator's seat in the aft section of the lower deck. Shortly after take-off, another cushion was placed under the seat. The flight was uneventful until the scheduled mid-air refueling from a KC-135 Stratotanker, which had to be conducted manually because of an error with the B-52G's autopilot. About one hour after refueling, while the aircraft was circling above its designated area, Captain Haug directed co-pilot Svitenko to take his rest period. His seat was taken by the spare pilot, D'Mario. The crew was uncomfortable because of the cold, although the heater's rheostat was turned up, so D'Mario opened an engine bleed valve to draw additional hot air into the heater from the engine manifold. Because of a heater malfunction, the air barely cooled as it traveled from the engine manifold to the cabin's heating ducts. During the next half-hour, the cabin's temperature became uncomfortably hot, and the stowed cushions ignited. After one crew member reported smelling burning rubber, they looked for a fire. The navigator searched the lower compartment twice before discovering the fire behind a metal box. He attempted to fight it with two fire extinguishers, but could not put it out.
At 15:22 EST, about six hours into the flight and 90 miles (140 km) south of Thule Air Base, Haug declared an emergency. He told Thule air traffic control that he had a fire on board and requested permission to perform an emergency landing at the air base. Within five minutes, the aircraft's fire extinguishers were depleted, electrical power was lost and smoke filled the cockpit to the point that the pilots could not read their instruments. As the situation worsened, the captain realized he would not be able to land the aircraft and told the crew to prepare to abandon it. They awaited word from D'Mario that they were over land, and when he confirmed that the aircraft was directly over the lights of Thule Air Base, the four crewmen ejected, followed shortly thereafter by Haug and D'Mario. The co-pilot, Leonard Svitenko, who had given up his ejection seat when the spare pilot took over from him, sustained fatal head injuries when he attempted to bail out through one of the lower hatches.
The pilotless aircraft initially continued north, then turned left through 180° and crashed onto sea ice in North Star Bay at a relatively shallow angle of 20 degrees—about 7.5 miles (12.1 km) west of Thule Air Base—at 15:39 EST. The conventional high explosive (HE) components of four 1.1 megaton B28FI thermonuclear bombs detonated on impact, spreading radioactive material over a large area in a manner similar to a dirty bomb. "Weak links" in the weapon design ensured that a nuclear explosion was not triggered. The extreme heat generated by the burning of 225,000 pounds (102 t) of jet fuel during the five to six hours after the crash melted the ice sheet, causing wreckage and munitions to sink to the ocean floor.
Haug and D'Mario parachuted onto the grounds of the air base and made contact with the base commander within ten minutes of each other. They informed him that at least six crew ejected successfully and the aircraft was carrying four nuclear weapons. Off-duty staff were mustered to conduct search and rescue operations for the remaining crew members. Owing to the extreme weather conditions, Arctic darkness, and unnavigable ice, the base relied largely on the Thule representative of the Royal Greenland Trade Department, Ministry of Greenland, Jens Zinglersen, to raise and mount the search 
1968 Thule Air Base B-52 crash