Air Force-wide as "Dumbo" and "Plumber's Nightmare", and among ATC crews as the "flying coffin". In its first five months of operations, 20% of the C-46s assigned to the airlift crashed. When it first arrived in theater, in addition to being accompanied by technical orders that required 50 field modifications before it could be flown operationally, the C-46 also required additional training for inexperienced crews, and a transition school was established that drained the airlift of ten aircraft and crews. Worse, spare parts were in such scarce supply until the fall of 1943 that 26 of the first 68 C-46s sent were out of commission. Flight hazards Flying over the Hump proved to be an extremely hazardous undertaking for Allied flight crews. The air route wound its way into the high mountains and deep gorges between north Burma and west China, where violent turbulence, 125 to winds, icing, and inclement weather conditions were a regular occurrence. Lack of suitable navigational equipment, radio beacons, and inadequate numbers of trained personnel (there were never enough navigators for all the groups) continually affected airlift operations. In the first year of the airlift, inexperienced officers of the Services of Supply often ordered planes loaded until they were "about full", ignorant of gross weight limitations or center of gravity placement, while most pilots were reserves recently called up from the airlines with little military transport experience and accustomed to civilian safety standards. As the airlift grew in size and scope in 1943, demands of tactical units and the failure of airline-conducted ATC training programs to produce sufficient multi-engined pilots limited nearly all reinforcement pilots to those just out of flight school or single-engine rated pilots from training fields who had relatively little instrument time. In December 1942, one-third of the 102 technical sergeant (non-commissioned officer) pilot training graduates of the Lubbock Field Class 42-I were immediately sent to India to fly the Hump as replacement co-pilots. This collective inexperience required ICW to create an in-theater OTU near Karachi to qualify new arrivals, taking 16 experienced pilots and eight to ten aircraft away from the airlift. CNAC pilots, while accustomed to a variety of aircraft, also had little instrument experience, and most were unfamiliar with the large American transport aircraft used in the airlift. Not until 1944, when the ATC recruited high hour civilian flight instructors released by the USAAF in pilot training program cutbacks, and