This additional development increased the utility of the aircraft and its variants to allow it to perform a number of unique tasks, including the HC-123B which operated with the USCG fitted with additional radar equipment for search and rescue missions through 1971, and the C-123J which was fitted with retractable skis for operations in Greenland and Alaska on compacted snow runways.

[10] Installation of a dome on the nose of the aircraft accommodated a large radar allowing the plane to meet the requirements for search and rescue and long range flight over water.

In 1979, the Royal Thai government, seeking to extend the life of their C-123 fleet, placed a contract with the Mancro Aircraft Company, supported by the USAF, to convert a single C-123B to turboprop powerplants.

[citation needed] Budgetary restrictions forced the Thai government to abandon the program in 1981, and with a lack of interested parties development of the C-123T stopped.

[citation needed] However, it concluded the life of the C-123 by making it the only aircraft type to operate under jet, piston, and turboprop engine power, and as a glider, during its history.

The "Candle" aircraft had an extended life when several UC-123Ks were transferred to Nakhon Phanom Royal Thai Air Force Base in Thailand.

The flare duties were generally used for troops in contact (TIC) while the FAC mission directed air strikes in Laos over the Ho Chi Minh trail.

Another NC-123B was used as a radio relay aircraft over the Ho Chi Minh trail, with equipment to read the signals from various sensors on the ground designed to pick up enemy truck activity.

[17] The Black Spot aircraft were to fit under the "self-contained night attack capability" that was Operation Shed Light's primary focus and E-Systems of Greenville, Texas, was contracted to complete the modifications.

These aircraft featured a variety of new sensors including Low Light Level TV (LLLTV), Forward Looking Infrared (FLIR), and a laser rangefinder.

[18] The aircraft looked radically different visibly from its transport brethren, as the new equipment required lengthening the nose by over 50 inches (127 cm).

The five Taiwan C-123Bs were sent to Lockheed Skunk Works for modifications as covert insertion aircraft with "smart" air-to-air jammer, BSTR system to jam the radars of ground anti-aircraft guns, also added a defensive operator's station to operate the jammers on board, with extra fuel in underwing tanks, with 36 Taiwanese crew finished training courses at Pope AFB by November 1962.

The five ROCAF/Taiwan/CIA C-123Bs would be used over North Vietnam as low level and nighttime covert airdrop aircraft, under the South Star II agreement, under the guise of Taiwan's national airline, China Airlines, which had "cover story" of operating Vietnamese Air Transport (VIAT) in South Vietnam, that was formerly operated by Air America.

On 1 February 1964, the overall control of South Star II was transferred from CIA to Studies and Observations Group (SOG), as part of U.S. Military Assistance Command Vietnam (MACV) in Saigon.

The "Duck Hook" C-123Bs were updated with RDR-10 weather radar and ARN-131 homing receiver in 1966 in order to perform missions over the Ho Chi Minh trail.

[24] On 5 October 1986, a Corporate Air Services C-123 Provider (HPF821, previously N4410F and USAF 54-679, (c/n 20128))[25] departed San Salvador-Ilopango Airport in El Salvador loaded with 70 AK-47 rifles and 100,000 rounds of ammunition, rocket grenades and other supplies.

Its sister ship, also a Fairchild C-123 that was purchased by the CIA at the same time as the first one, was then left abandoned at San Jose International Airport for a time and then was purchased for $3,000 and disassembled into 7 pieces and transported via boat to Quepos, Costa Rica and then reassembled and is now the center piece of a beachside cocktail lounge just up the road from Manual Antonio national park.

In his complaint, Major Carter contends that the Air Force has known since 1994 that the aircraft were contaminated with the defoliant; he cites the fact that when a former C-123 was being prepared for a permanent static display that workers had to use HAZMAT suits and respirators.

[citation needed] The aircraft which were flown from 1972–1982, were assigned to the Air Force Reserve after their service in Vietnam, and used for normal cargo and aeromedical evacuation missions.

Air crews accumulated hundreds of flight hours aboard several contaminated aircraft that were often flown with the windows open due to the smell and eye irritation.

Memos surfaced showing that Air Force JAG officers recommended keeping the toxicity information, "...within official channels."

In 2010, due to concerns about dioxin contamination, the Air Force took the unusual step of shredding all the remaining surplus C-123K/UC-123K aircraft and melting the scraps into ingots for disposal.

[28] On 9 June 2011, the Secretary of the U.S. Air Force's Inspector General rejected Carter's complaints, and in a subsequent message explained, "Unfortunately, we do not have the ability to identify or notify the individuals in the categories you mention" when asked if the military would alert the aircrews regarding their exposure to dioxin.

[29] In December 2011, the U.S. Department of Veterans Affairs posted two notices of its decision that, while the post-Vietnam aircraft "may" have been contaminated, the aircrews were "unlikely" to have suffered exposure to dioxin.

In an unusual response, the U.S. Center for Toxic Substance and Disease Registry quickly countered the VA position on 25 January 2012 with a statement by their Deputy Director concluding that aircrews and maintenance personnel most likely were exposed well beyond military and government surface-wipe screening levels.

[30] Several other examples of C-123s remain in an active flying status, operated by private owners in the United States or by various air forces worldwide.

[72][73] Data from The Observer's Book of Basic Aircraft: Military (dimensions),[74] Jane's All The World's Aircraft 1969–70 (weights and performance)[75]General characteristics Performance A C-123K (54-709), N709RR (since destroyed in a crash in 2010) was prominently featured in the action film Con Air (1997); other C-123s appeared in Air America (1990), Outbreak (1995), Operation Dumbo Drop (1995) and American Made (2017), none of which were used in Operation Ranch Hand.