As the month of April went on, Saigon sweltered in the pre-monsoon heat, and the North Vietnamese came closer.
I quote from Wikipedia:
On the afternoon of Friday, 4 April 1975, C-5A, AF Ser. No. 68-0218, making the first flight of OPERATION BABYLIFT, departed Tan Son Nhut . . . . At 4:15 p.m. the C-5A was over the South China Sea about 13 nautical miles (24 km) off Vũng Tàu, South Vietnam, flying a heading of 136 degrees and climbing to an altitude of 23,000 ft (7,010 m). At that moment the locks on the rear loading ramp failed, causing the cargo door to open explosively. This caused explosive decompression, temporarily filling the cabin with a whirlwind of fog and debris. The blowout severed control cables to the tail, causing two of four hydraulic systems to fail, including those for the rudder and elevator, and leaving the flight control with only the use of one aileron, spoilers, and power.
The pilot, Captain Dennis “Bud” Traynor, and copilot, Captain Tilford Harp, attempted to regain control of the airplane, and to perform a 180 degree turn in order to return to Tan Son Nhut. The aircraft began to exhibit phugoid oscillations, but the crew countered them and maintained a controlled descent of about 250 to 260 knots (460 to 480 km/h). They were able to bring the plane to 4,000 ft (1,220 m) and begin the approach to Tan Son Nhut’s runway 25L. While turning on final approach, the plane’s descent rate suddenly began to increase rapidly. The crew increased power to the engines in an attempt to arrest the descent, but despite their efforts, the plane touched down at 4:45 p.m. in a rice paddy, and skidded for a quarter of a mile (400 m), became airborne again for another half-mile (800 m), crossing the Saigon River, then hit a dike and broke up into four pieces. The fuel caught fire and some of the wreckage was set ablaze.