A critical problem proved to be finding a cargo aircraft capable of carrying heavy payloads at the high altitudes required, and three types were tried before the opening of a low Hump route permitted the use of C-54s: C-47 and variants, C-46, and C-87/C-109.

Initially, the India-China airlift was flown with the Douglas DC-3 and its military versions, the C-47, C-53 and C-39.
However, the DC-3 design's fuselage was so high off the ground that loading from most truck beds was difficult, and its narrow door and weak floor could not sustain heavy cargo.
Although C-47s had reinforced flooring and a wider door, they still required specialized loading equipment for much of the cargo needed in China and had a limited payload capacity.
Also, performance specifications of the Douglas transports were not suited to high-altitude operation with heavy payloads, and could not normally reach an altitude sufficient to clear the mountainous terrain, forcing the planes to attempt a highly dangerous route through the maze-like Himalayan passes.

The introduction in January 1943 of the Consolidated C-87 Liberator Express, a design modification of the B-24D heavy bomber, boosted tonnage figures.
Its high-altitude capability enabled it to surmount the lower mountains (15,000–16000 feet MSL) without resorting to the passes, but the type had a high accident rate and was unsuited to the airfields then in use.
Despite having four engines, the C-87 climbed poorly with heavy loads, as did its bomber counterparts, and often crashed on takeoff if an engine was lost.
Its poor cockpit illumination was inadequate for bad weather flying and often failed during instrument takeoffs, its electrical and hydraulic systems frequently froze at high altitude and malfunctioned, and its flight deck heating system was prone to produce either stifling heat or none at all.
Attributed by its pilots to its slim Davis wing, the C-87 also had a tendency to spin out of control when encountering even mild icing conditions over the mountains.
One Hump pilot called the variant "an evil, bastard contraption" and a "ground-loving bitch" that "could not carry enough ice to chill a highball".

Despite its shortcomings, the C-87 was valued for the reliability of its engines, speed that enabled it to reduce significantly the effect of head and cross winds, a service ceiling that allowed it to surmount most weather fronts, and range that permitted its crews to fly "pressure-front" patterns that chased favorable winds.

Another Liberator transport variant, the C-109, carried gasoline in converted B-24Js or B-24Ls.
All combat equipment was removed and eight flexible bag fuel tanks were installed inside the fuselage with a 2,900 U.S. gallon capacity.
70 were initially planned to fly the Hump with XX Bomber Command, beginning in September 1944, but most of the 218 C-109 conversions eventually served in the CBI under ATC after B-29 operations were shifted from China back to India.
At least 80 were involved in major accidents between September 1944 and August 1945.
Like the C-87, they were not popular with their crews, since they were very difficult to land when fully loaded, particularly at airfields such as Kunming's above 6,000 feet (1,800 m) in elevation, and often demonstrated unstable flight characteristics when all eight cargo tanks were full.
A crash landing of a loaded C-109 inevitably resulted in an explosion and crew fatalities, earning it the nickname "C-One-Oh-Boom".

The Curtiss C-46 Commando began to fly India-China missions in May 1943.
The C-46 was a large twin-engine aircraft capable of flying faster and higher than any previous medium-range cargo aircraft, and could carry heavier loads than either the C-47 or the C-87, albeit at two and one half times the unit cost for a C-47.
With the C-46, airlift tonnage increased significantly, surpassing objectives with 12,594 tons in December 1943.
Loads continued to increase throughout 1944 and 1945, reaching an all-time maximum tonnage in July 1945.
Performance of the Commando was enhanced when camouflage paint, standard on all AAF
A critical problem proved to be finding a cargo aircraft capable of carrying heavy payloads at the high altitudes required, and three types were tried before the opening of a low Hump route permitted the use of C-54s: C-47 and variants, C-46, and C-87/C-109.
Initially, the India-China airlift was flown with the Douglas DC-3 and its military versions, the C-47, C-53 and C-39. However, the DC-3 design's fuselage was so high off the ground that loading from most truck beds was difficult, and its narrow door and weak floor could not sustain heavy cargo. Although C-47s had reinforced flooring and a wider door, they still required specialized loading equipment for much of the cargo needed in China and had a limited payload capacity. Also, performance specifications of the Douglas transports were not suited to high-altitude operation with heavy payloads, and could not normally reach an altitude sufficient to clear the mountainous terrain, forcing the planes to attempt a highly dangerous route through the maze-like Himalayan passes.
The introduction in January 1943 of the Consolidated C-87 Liberator Express, a design modification of the B-24D heavy bomber, boosted tonnage figures. Its high-altitude capability enabled it to surmount the lower mountains (15,000–16000 feet MSL) without resorting to the passes, but the type had a high accident rate and was unsuited to the airfields then in use. Despite having four engines, the C-87 climbed poorly with heavy loads, as did its bomber counterparts, and often crashed on takeoff if an engine was lost. Its poor cockpit illumination was inadequate for bad weather flying and often failed during instrument takeoffs, its electrical and hydraulic systems frequently froze at high altitude and malfunctioned, and its flight deck heating system was prone to produce either stifling heat or none at all. Attributed by its pilots to its slim Davis wing, the C-87 also had a tendency to spin out of control when encountering even mild icing conditions over the mountains. One Hump pilot called the variant "an evil, bastard contraption" and a "ground-loving bitch" that "could not carry enough ice to chill a highball".
Despite its shortcomings, the C-87 was valued for the reliability of its engines, speed that enabled it to reduce significantly the effect of head and cross winds, a service ceiling that allowed it to surmount most weather fronts, and range that permitted its crews to fly "pressure-front" patterns that chased favorable winds.
Another Liberator transport variant, the C-109, carried gasoline in converted B-24Js or B-24Ls. All combat equipment was removed and eight flexible bag fuel tanks were installed inside the fuselage with a 2,900 U.S. gallon capacity. 70 were initially planned to fly the Hump with XX Bomber Command, beginning in September 1944, but most of the 218 C-109 conversions eventually served in the CBI under ATC after B-29 operations were shifted from China back to India. At least 80 were involved in major accidents between September 1944 and August 1945. Like the C-87, they were not popular with their crews, since they were very difficult to land when fully loaded, particularly at airfields such as Kunming's above 6,000 feet (1,800 m) in elevation, and often demonstrated unstable flight characteristics when all eight cargo tanks were full. A crash landing of a loaded C-109 inevitably resulted in an explosion and crew fatalities, earning it the nickname "C-One-Oh-Boom".
The Curtiss C-46 Commando began to fly India-China missions in May 1943. The C-46 was a large twin-engine aircraft capable of flying faster and higher than any previous medium-range cargo aircraft, and could carry heavier loads than either the C-47 or the C-87, albeit at two and one half times the unit cost for a C-47. With the C-46, airlift tonnage increased significantly, surpassing objectives with 12,594 tons in December 1943. Loads continued to increase throughout 1944 and 1945, reaching an all-time maximum tonnage in July 1945. Performance of the Commando was enhanced when camouflage paint, standard on all AAF 
The Hump