Fairchild C-123K Provider, apparently still flying, at Kingman Airport AZ.
The C-123K had a remarkable service record in Southeast Asia the highlight of which was 179 missions flown into the beleaguered American Combat base at Khe Sanh, Vietnam during the three-month siege by North Vietnamese troops. On February 12th, 1968, all C-130 Hercules operations were suspended.
The C-123 Providers of the 315th Special Operations Wing were the only fixed-wing transports to continue operation into the base. Two examples of the NC-123K, also known as AC-123K, were produced. These aircraft were highly modified for night surveillance missions in SEA. AF 54-0691 and 54-0698 were modified by Ling-Temco-Vought during 1966 with an extended nose shape that contained "Black Spot" sensors for these special missions.
Several C-123s were used as VIP transports. The best known of these was "The White Whale" (AF 56-4375). General Westmoreland used this aircraft as his personal transport in Southeast Asia. Other VIP conversions operated in the embassy support role at scattered locations around the globe.
Canadian Aviation Blog