During the siege, the U.S. Air Force flew an average of 11 three-plane B-52 formations per day, and Air Force, Marine and Navy fighter aircraft averaged some 300 attacks daily. Two-thirds of the fighters dropped bombs or napalm under radar direction from the base. Night bombing runs were conducted using flares, and the night skies around the base were patrolled by AC-47 and AC-130 gunships armed with cannons and miniguns.

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The NVA knew the B-52s were restricted from dropping within a mile of friendly forces, so at night they tried to move at least that close to the perimeter. When, on February 29, the B-52s reduced the stand-off distance from the perimeter to one-half mile, the result was the decimation of an NVA two-battalion attack force. During the course of the siege, the U.S. Air Force dropped five tons of bombs for each of the estimated 20,000 attacking NVA troops.

If firepower determined the outcome of the fight, it was airlift that allowed the defenders to hold their positions. Since late in 1967, Khe Sanh had depended on airlift for its survival. When the siege began on January 21, the loss of the main ammunition dump and the cutting of the runway threatened disaster, but that same day, despite bad weather, C-123s airlanded four tons of supplies and C-130s began airdrops, while Marine helicopters took the wounded off the hilltop firebases.

From the very beginning, helicopter support was crucial. When they could no longer be based at Khe Sanh Combat Base, helicopters operated from Dong Ha and other nearby locations. Throughout the siege, they braved enemy fire on approach and departure as well as mortar, rocket and artillery fire when on the ground. They augmented the fixed-wing aircraft in supplying the main base and were vital in rotating personnel and evacuating the wounded. Helicopters provided the only direct support to the hilltop firebases, bringing in all supplies, including precious trailer loads of water. Seventeen helicopters went down during the siege and another 35 were badly damaged. Using primarily Marine CH-46s and CH-53s, most of the resupply missions were flown using external slings with up to two tons of cargo in each net. Fully aware of being easy targets, the helicopter crews were limited to as little as 19 seconds’ hover time for their deliveries. Beginning in late February until the end of the siege, supply helicopters flew in formations of 12—called Super Gaggles—escorted by fighters and helicopter gunships. During bad weather the crews used flares, smoke and multiple de­scents to find their designated landing zones.

Without control of the hills, Khe Sanh might have turned into another Dien Bien Phu, and without the helicopters the hill firebases could not have survived.

An average of 155 tons of supplies was landed or dropped each day of the siege. Thirty-five percent of the tonnage was landed, with C-130s delivering 60 percent of that amount and C-123s, with their shorter landing roll, bringing in the rest. The C-123s carried three- to five-ton loads, while the larger C-130s delivered 10 to 15 tons per sortie. Both aircraft had floor-roller assemblies and palletized cargo systems for rapid on- and off-load and were capable of flying multiple sorties per day. Cargo reload points included Saigon and Bien Hoa to the south, and the nearby airlift depot at Da Nang, only a 30-minute flight from Khe Sanh.

The normal approach to the Khe Sanh runway was from the east, which was facilitated by instrument approach to touchdown. But the eastern approach was directly over NVA-held territory and left the aircraft vulnerable to intense groundfire both coming and going. The NVA at Khe Sanh had no SAMs or high-velocity/high-­altitude/radar-guided guns, but the volume of fire from handheld and crew-served weapons was stil formidable. Two C-123s and one C-130 were lost during the siege.

The crews used the eastern approach whenever the weather screened the aircraft from groundfire. Otherwise, the transports made a sharply turned, steeply banked, short downwind visual approach to the western end of the runway. The groundfire was less, but so was the terrain clearance.

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