William Caldwell was born on August 20, 1943, in Illinois. He was commissioned through the Air Force ROTC program on September 7, 1967, and went on active duty beginning December 10, 1967. Lt Caldwell completed Undergraduate Pilot Training and was awarded his pilot wings at Laredo AFB, Texas, in April 1969, and then flew C-130 Hercules transports with the 778th Tactical Airlift Squadron (TAS) at Pope AFB, North Carolina, from May 1969 to April 1971. He next deployed to Southeast Asia, where he flew C-130's with the 776th TAS at Ching Chuan Kang AB, Taiwan, from April 1971 to June 1972, followed by service with the 40th TAS at Pope AFB from June 1972 to October 1973. Capt Caldwell served as a Flying Safety Officer with the 317th Tactical Airlift Wing (TAW) at Pope from November 1973 to July 1975, and then served with Headquarters Military Airlift Command at Scott AFB, Illinois, from July 1975 to July 1978. His next assignment was as an aircraft commander and chief instructor pilot with the 772nd TAS at Dyess AFB, Texas, from July 1978 to October 1980, and then as chief of tactics and techniques with the 463rd TAW at Dyess from October 1980 to November 1982. Col Caldwell served a tour with Headquarters U.S. Air Force in the Pentagon from December 1982 to September 1985, followed by service as a C-130 aircraft commander with the 61st TAS at Little Rock AFB, Arkansas, from September 1985 to February 1986. He was commander of the 62nd TAS at Little Rock from February 1986 to December 1987, and then served as deputy commander for operations of the 316th Tactical Airlift Group at Yokota AB, Japan, from December 1987 to July 1989. His final assignment was on the staff of Headquarters Military Airlift Command (renamed Air Mobility Command in June 1992) at Scott AFB, where he served as deputy director of tactics, director of advanced combat concepts, and chief of the combat operations and training division from July 1989 until his retirement from the Air Force on October 1, 1993.

His Air Force Cross Citation reads:

The President of the United States of America, authorized by Title 10, Section 8742, United States Code, takes pleasure in presenting the Air Force Cross to Colonel William R. Caldwell, United States Air Force, for extraordinary heroism in military operations against an opposing armed force as a C-130E Instructor Pilot for the 776th Tactical Airlift Squadron, An Loc Air Base, Vietnam, in action at An Loc, Republic of Vietnam, on 15 April 1972. On that date, Captain Caldwell flew a tactical emergency airdrop of critically needed ammunition to a besieged concentration of allied forces located in a heavily defended area. En route to the target, his aircraft was severely damaged by hostile anti-aircraft fire, fatally injuring the Flight Engineer and wounding other crew members. Realizing bailout of the injured crew members would be extremely difficult, Captain Caldwell, without regard for his personal safety, remained at his station and flew the aircraft to a successful two-engine landing, thereby saving the lives of his crew. Through his extraordinary heroism, superb airmanship, and aggressiveness in the face of the enemy, Captain Caldwell reflected the highest credit upon himself and the United States Air Force.