Even under ideal circumstances, the airlift would have been a massive undertaking. The difficulties, however, were compounded by the poor visibility which was below minimum for airfield operations 40 percent of the time and the heavy volume of antiaircraft and artillery fire directed at the incoming transports. The NVA had moved several antiaircraft units into the hills east of the airstrip forcing the C-130 Hercules, the C-123 Providers, and the helicopters to run the gauntlet during their final approach. Under cover of the heavy fog, some audacious NVA gun crews positioned their antiaircraft weapons just off the eastern threshold of the runway and fired in the blind whenever they heard the drone of incoming planes. Several aircraft were hit while on GCA final and completely in the soup.[35](116) Immediately after touchdown, the aircraft were subjected to intense mortar and rocket fire; in fact, the incoming was so closely synchronized with their arrival, the fixed-wing transports were nicknamed "mortar magnets" by the Marines.(117) [Illustration: View of airstrip at Khe Sanh facing east. (Photo courtesy David D. Duncan)] [Illustration: U. S. Air Force C-130 about to touch down after approaching from the east. (Photo courtesy David D. Duncan)] The key to survival for the pilots was a steep approach through the eastern corridor, a short roll-out, and a speedy turnaround after landing. A small ramp paralleled the western end of the strip which the transport crews used as an unloading point. After roll-out, the pilot turned off the runway onto the easternmost taxiway, then wheeled onto the ramp while the loadmasters shoved the pallets of supplies out the back.[36] All outgoing passengers were loaded on the double because the planes rarely stopped rolling. The pilot completed the loop by turning back onto the runway via the western taxiway and took off in the opposite direction from which he landed. It was not uncommon for the entire circuit to be completed within three minutes; even then, the planes were tracked by exploding mortar rounds.(118)