NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

WHILE IN CRUISE FLIGHT AT FLIGHT LEVEL 310, 20 MILES WEST OF DENVER, COLORADO, THE ALL CARGO 14 CFR PART 121 FLIGHT ENCOUNTERED SEVERE CLEAR AIR TURBULENCE WHICH CAUSED MAJOR FLUCTUATIONS IN SPEED AND OSCILLATIONS IN BOTH PITCH AND ROLL. DURING THESE DEPARTURES FROM CONTROLLED FLIGHT, THE NUMBER ONE ENGINE AND 19 FEET OF THE LEADING EDGE OF THE LEFT WING SEPARATED FROM THE AIRCRAFT. IN ADDITION, THE NUMBER FOUR ENGINE PYLON CRACKED AND EXPERIENCED SUBSTANTIAL STRUCTURAL DAMAGE. THE FLIGHT CONDUCTED A PRECAUTIONARY DESCENT AND LANDED AT STAPLETON INTERNATIONAL AIRPORT, DENVER, COLORADO. PRECEDING THE OCCURRENCE, THE FLIGHT WAS ENCOUNTERING LIGHT TO OCCASIONALLY MODERATE CHOP, WITH MODERATE TO SEVERE TURBULENCE FORECAST.