Blood being processed for Americans during Korean War

The transcript describes the logistics of transporting blood from the United States to Korea during wartime. Blood is preserved for 21 days and must be repacked in ice. Relay teams ensure its delivery across the Pacific. The efficient schedule allows blood to reach the front lines within six days. Helicopters play a crucial role, delivering blood and transporting wounded soldiers back.

Describe the function of helicopters in the blood delivery system mentioned in the text.

What happens to the helicopter's cargo after delivering blood at the front?