The F-100A officially entered USAF service on 27 September 1954, with the 479th Fighter Wing at George AFB, California. By 10 November 1954, the F-100As suffered six major accidents due to flight instability, structural failures, and hydraulic system failures, prompting the air force to ground the entire fleet until February 1955. The 479th finally became operational in September 1955. Due to ongoing problems, the air force began phasing out the F-100A in 1958, with the last aircraft leaving active duty in 1961. By that time, 47 aircraft had been lost in major accidents. Escalating tension due to construction of the Berlin Wall in August 1961 forced the USAF to recall the F-100As into active service in early 1962. The aircraft was finally retired in 1970.
The TAC request for a fighter-bomber was addressed with the F-100C which flew in March 1954 and entered service on 14 July 1955, with the 450th Fighter Wing, Foster AFB, Texas. Operational testing in 1955 revealed that the F-100C was at best an interim solution, sharing all the flaws of the F-100A. The uprated J57-P-21 engine boosted performance but continued to suffer from compressor stalls. However, the F-100C was considered an excellent platform for nuclear toss bombing because of its high top speed. The inertia coupling problem was reasonably addressed with the installation of a yaw damper in the 146th F-100C, later retrofitted to earlier aircraft. A pitch damper was added starting with the 301st F-100C, at a cost of US$10,000 per aircraft.
The addition of "wet" hardpoints meant the F-100C could carry a pair of 275 U.S. gal (1,040 l) and a pair of 200 U.S. gal (770 l) drop tanks. However, the combination caused a loss of directional stability at high speeds and the four tanks were soon replaced by a pair of 450 U.S. gal (1,730 l) drop tanks. The 450s proved scarce and expensive and were often replaced by smaller 335 US gal (1,290 l) tanks. Most troubling to TAC was the fact that, as of 1965, only 125 F-100Cs were capable of utilizing all non-nuclear weapons in the air force inventory, particularly cluster bombs and AIM-9 Sidewinder air-to-air missiles. By the time the F-100C was phased out in June 1970, 85 had been lost in major accidents.
The definitive F-100D aimed to address the offensive shortcomings of the F-100C by being primarily a ground attack aircraft with secondary fighter capabilities. To this effect, the aircraft was fitted with autopilot, upgraded avionics, and, starting with the 184th production aircraft, AIM-9 Sidewinder capability. In 1959, 65 aircraft were modified to also fire the AGM-12 Bullpup air-to-ground missile. To further address the dangerous flight characteristics, the wing span was extended by 26 in (66 cm) and the vertical tail area was increased by 27%.
The first F-100D (54–2121) flew on 24 January 1956, piloted by Daniel Darnell. It entered service on 29 September 1956 with the 405th Fighter Wing at Langley AFB. The aircraft suffered from reliability problems with the constant speed drive which provides constant-frequency current to the electrical systems. In fact, the drive was so unreliable that the USAF required it to have its own oil system to minimize damage in case of failure. Landing gear and brake parachute malfunctions claimed a number of aircraft, and the refueling probes had a tendency to break away during high speed maneuvers. Numerous post-production fixes created such a diversity of capabilities between individual aircraft that, by 1965, around 700 F-100Ds underwent High Wire modifications to standardize the weapon systems. High Wire modifications took 60 days per aircraft at a cost for the entire project of US $150 million. In 1966, the Combat Skyspot program fitted some F-100Ds with an X band radar transmitter to allow for ground-directed bombing in inclement weather or at night.
In 1961, at England AFB, Louisiana, (401st Tactical Wing), there were four fighter-bomber squadrons. These were the 612th, 613th, 614th and the 615th (Fighting Tigers). During the Berlin Crisis (approximately September 1961) the 614th was deployed to Ramstein Air Base, Germany, to support the West Germans. At the initial briefing, the 614th personnel were informed that, due to the close proximity of the USSR, if an ICBM were to be launched, they would have only 30 minutes to launch the 614th's aircraft and retire to the nearest German bunker.
In 1967, the USAF began a structural reinforcement program to extend the aircraft's service life from the designed 3,000 flying hours to 7,000. The USAF alone lost 500 F-100Ds, predominantly in accidents. After one aircraft suffered wing failure, particular attention was paid to lining the wings with external bracing strips. During the Vietnam War, combat losses constituted as many as 50 aircraft per year. On 7 June 1957, an F-100D fitted with an Astrodyne booster rocket making 150,000 lbf (667.2 kN) of thrust successfully performed a zero length launch (ZeLL). This was accomplished with the addition of a large canister to the underside of the aircraft. This canister contained a black powder compound and was ignited electro-mechanically, driving the jet engine to minimal ignition point. The capability was incorporated into late-production aircraft. After a major accident, the USAF Thunderbirds reverted from F-105 Thunderchiefs to the F-100D which they operated from 1964 until it was replaced by the F-4 Phantom II in 1968.
The F-100 was the subject of many modification programs over the course of its service. Many of these were improvements to electronics, structural strengthening, and projects to improve ease of maintenance. One of these was the replacement of the original afterburners of the J-57 engines with the more advanced afterburners from retired Convair F-102 Delta Dagger interceptors. This modification changed the appearance of the aft end of the F-100, doing away with the original "petal-style" exhaust. The afterburner modification started in the 1970s and solved maintenance problems with the old type as well as operational problems, including compressor stall issues.
The F-100F two-seat trainer entered service in 1958. It received many of the same weapons and airframe upgrades as the F-100D, including the new afterburners. By 1970, 74 F-100Fs were lost in major accidents.
By 1972, the F-100 was mostly phased out of USAF active service and turned over to tactical fighter groups and squadrons in the ANG. In Air National Guard units, the F-100 was eventually replaced by the F-4 Phantom II, LTV A-7 Corsair II, and A-10 Thunderbolt II, with the last F-100 retiring in 1979, with the introduction of the F-16 Fighting Falcon. In foreign service, the Royal Danish Air Force and Turkish Air Force F-100s soldiered on until 1982.
Over the lifetime of its USAF service, a total of 889 F-100 aircraft were destroyed in accidents, involving the deaths of 324 pilots. The deadliest year for F-100 accidents was 1958, with 116 aircraft destroyed, and 47 pilots killed.
After Super Sabres were withdrawn from service, a large number were converted into remote-controlled drones (QF-100) under the USAF Full Scale Aerial Target (FSAT) program for use as targets for various anti-aircraft weapons, including missile-carrying fighters and fighter-interceptors, with FSAT operations being conducted primarily at Tyndall AFB, Florida. A few F-100s also found their way into civilian hands, primarily with defense contractors supporting USAF and NASA flight test activities at Edwards AFB, California.
On 16 April 1961, six Super Sabres were deployed from Clark Air Base in the Philippines to Don Muang Airfield in Thailand for air defense purposes; the first F-100s to enter combat in Southeast Asia. From that date until their redeployment in 1971, the F-100s were the longest serving U.S. jet fighter-bomber to fight in the Vietnam War. Serving as MiG combat air patrol escorts for F-105 Thunderchiefs, Misty FACs, and wild weasels over North Vietnam, and then relegated to close air support and ground attacks within South Vietnam.
On 18 August 1964, the first F-100D shot down by ground fire, piloted by 1st Lt Colin A. Clarke, of the 428th TFS; Clarke ejected and survived. On 4 April 1965, as escorts protecting F-105s attacking the Thanh Hoa Bridge, F-100 Super Sabres fought the USAF's first air-to-air jet combat duel in the Vietnam War, in which an F-100 piloted by Captain Donald W. Kilgus shot down a North Vietnamese Air Force MiG-17, using cannon fire, while another fired Sidewinder missiles. The surviving North Vietnamese pilot confirmed three of the MiG-17s had been shot down. Although recorded by the U.S. Air Force as a probable kill, this represented the first aerial victory by the U.S. Air Force in Vietnam. However, the small force of four MiG-17s had penetrated the escorting F-100s to claim two F-105s. The F-100 was soon replaced by the F-4C for MiG CAP which pilots noted suffered for lacking built-in guns for dogfights.
The Vietnam War was not known for utilizing activated Army National Guard, Air National Guard or other U.S. Reserve units; but rather, had a reputation for conscription during the course of the war. During a confirmation hearing before Congress in 1973, USAF general, George S. Brown, who had commanded the 7th Air Force during the war, stated that five of the best Super Sabre squadrons in Vietnam were from the ANG. This included the 120th Tactical Fighter Squadron (120 TFS) of the Colorado Air National Guard, the 136 TFS of the New York Air National Guard TFS, the 174 TFS of the Iowa Air National Guard and the 188 TFS of the New Mexico Air National Guard. The fifth unit was a regular AF squadron manned by mostly air national guardsmen.
The Air National Guard F-100 squadrons increased the regular USAF by nearly 100 Super Sabres in theater, averaging, for the Colorado ANG F-100s, 24 missions a day, delivering ordnance and munitions with a 99.5% reliability rate. From May 1968 to April 1969, the ANG Super Sabres flew more than 38,000 combat hours and more than 24,000 sorties. Between them, at the cost of seven F-100 Air Guard pilots killed (plus one staff officer) and the loss of 14 Super Sabres to enemy action, the squadrons expended over four million rounds of 20mm shells, 30 million pounds of bombs and over 10 million pounds of napalm against their enemy.
The Hun was also deployed as a two-seat F-100F model which saw service as a "fast FAC" or Misty FAC (forward air controller) in North Vietnam and Laos, spotting targets for other fighter-bomber aircraft, performing road reconnaissance, and conducting SAR (search and rescue) missions as part of the top-secret project, Commando Sabre, based out of Phu Cat and Tuy Hoa air bases. It was also the first Wild Weasel SEAD (air defense suppression) aircraft whose specially trained crews were tasked with locating and destroying enemy air defenses. Four F-100F Wild Weasel Is were fitted with an APR-25 vector radar homing and warning (RHAW) receiver, IR-133 panoramic receivers with greater detection range, and KA-60 panoramic cameras. The APR-25 could detect early-warning radars and emissions from SA-2 Guideline tracking and guidance systems. These aircraft deployed to Korat Royal Thai Air Force Base, Thailand, in November 1965, began flying combat missions with the 388th Tactical Fighter Wing in December. They were joined by three more aircraft in February 1966. All Wild Weasel F-100Fs were eventually modified to fire the AGM-45 Shrike anti-radiation missile.
By the war's end, 242 F-100 Super Sabres had been lost in Vietnam, as the F-100 was progressively replaced by the F-4 Phantom II and the F-105 Thunderchief. The Hun had logged 360,283 combat sorties during the war and its wartime operations came to end on 31 July 1971. The four fighter wings with F-100s flew more combat sorties in Vietnam than over 15,000 P-51 Mustangs flew during World War II. After 1965, they did not fly into North Vietnam and mainly performed close air support missions. Despite the April 1965 dogfight, the air force classified the engagement as resulting in a "probable" kill, and no F-100 was ever officially credited with any aerial victories. No F-100 in Vietnam was lost to enemy fighters, but 186 were shot down by anti-aircraft fire, seven were destroyed from Vietcong attacks on airbases, and 45 crashed in operational incidents.
French Air Force Super Sabres might have flown combat missions, with strikes flown from bases within France against targets in Algeria. The planes were based at Rheims, refuelling at Istres on the return flight from attacking targets in Algeria. The F-100 was the main fighter-bomber in the French Air Force during the 1960s, until it was replaced by the Jaguar.
Turkish Air Force F-100 units were used during the Turkish invasion of Cyprus in 1974. Together with F-104G Starfighters, they provided close air support to Turkish ground troops and bombed targets around Nicosia.