WV-2s, redesignated EC-121s in 1962, served from 1954 to 1965 in two "barrier" forces, one off each coast of the North American continent.
The barrier forces consisted of 5 surface picket stations each manned by radar destroyer escorts and an air wing of WV-2s/EC-121s that patrolled the picket lines at 1,000–4,000 m (3,000–12,000 ft) altitude in 6- to 20-hour missions.
Their objective was to extend early warning coverage against surprise Soviet bomber and missile attacks as an extension of the DEW Line.

In April 1954 the first Lockheed Super Constellation (Model 1049C), WV-2 BuNo.
128323, was received at NAS Barbers Point by Airborne Early Warning (AEW) Squadron One (VW-1).

The Atlantic Barrier (BARLANT) consisted of 2 rotating squadron detachments sourced from AEW Squadron THIRTEEN (VW-13) and AEW Squadron FIFTEEN (VW-15) from NAS Patuxent River, Maryland and one squadron, AEW Squadron ELEVEN (VW-11), permanently based at Naval Station Argentia, Newfoundland.
Their mission was to fly orbits to the Azores and back.
There was an additional AEW Training Unit based at NAS Patuxent River for training flight crews and maintenance personnel.

BARLANT became operational on 1 July 1956 and flew continuous coverage until early 1965.
The Barrier was shifted to cover the approaches between Greenland, Iceland and the United Kingdom (GIUK) barrier in June 1961.
Aircraft from Argentia were staged through NAS Keflavik, Iceland, to extend coverage times.

The Pacific Barrier (BARPAC) received the first operational AEW squadron, Airborne Early Warning Squadron One (VW-1) and the first EC-121K aircraft.
AEW Squadron Three followed with AEW Squadrons Twelve, Fourteen and Sixteen.
In January 1958 VW-1 and VW-3 relocated to NAS Agana, Guam, M.I. where VW-1 continued its AEW commitments and VW-3 operational commitment was divided between AEW and Weather.
BARPAC became ops with AEW Squadron TWELVE (VW-12) based at NAS Barbers Point, Hawaii, operating from a deployment  base at NAS Midway on 1 July 1958 and later expanded to include AEW Squadrons FOURTEEN (VW-14) and SIXTEEN (VW-16).
Their orbits overlapped the radar picket stations of the ships of Escort Squadron Seven (CORTRON SEVEN), from roughly Adak Island to Midway.
Normally 5 WV-2s/EC-121s were required at any single time to provide coverage over the entire line.

The Hawaiian Barrier force operations were discontinued by September 1965 and their EC-121K aircraft placed in storage.
However, VW-1 continued operating until 1972 flying weather ops and supplying AEW to Naval forces in the Gulf of Tonkin.
USN C-121, EC-121, WC-121 and NC-121 operations continued until 1975 in 7 other squadrons and until 1982 in an 8th.
Some EC-121s were used in Vietnam, mirroring USAF EC-121 missions but orbiting the Gulf of Tonkin, as that was the USN's assigned area.

Fleet Air Reconnaissance Squadron ONE (VQ-1) and Fleet Air Reconnaissance Squadron TWO (VQ-2) operated EC-121M ELINT gathering aircraft at NAF Atsugi, Japan, and Naval Station Rota, Spain, respectively, until they transitioned to the EP-3B Orion and EP-3E Aries aircraft.

Weather Reconnaissance Squadron FOUR (VW-4) operated WV-3-cum-WC-121s between 1954 and 1975 as Hurricane Hunters, with its primary base at NAS Jacksonville, Florida and a forward base at Naval Station Roosevelt Roads, Puerto Rico.
Its Pacific counterpart, Weather Reconnaissance Squadron Three (VW-3) Typhoon Trackers was the operational weather squadron in the Pacific, flying from NAS Agana, Guam, tracking typhoons from 1955 to 1960.
On June 30, 1960 Weather Reconnaissance Squadron Three, VW-3, disbanded and many of its aircraft (8 - BuNo.
145 series) and crews were absorbed by VW-1, which retained AEW designation and took on the weather commitments and the Title of "Typhoon Trackers" of VW-3.
 VW-4 later transitioned to  WP-3A Orion.

Also operating C-121 and EC-121 aircraft was Oceanographic Development Squadron EIGHT (VXN-8) at NAS Patuxent River, Maryland, which employed the aircraft for specific projects (e.g., Project BIRDSEYE, MAGNET, ASWEPS etc.)
for the Office of Naval Rese
WV-2s, redesignated EC-121s in 1962, served from 1954 to 1965 in two "barrier" forces, one off each coast of the North American continent. The barrier forces consisted of 5 surface picket stations each manned by radar destroyer escorts and an air wing of WV-2s/EC-121s that patrolled the picket lines at 1,000–4,000 m (3,000–12,000 ft) altitude in 6- to 20-hour missions. Their objective was to extend early warning coverage against surprise Soviet bomber and missile attacks as an extension of the DEW Line.
In April 1954 the first Lockheed Super Constellation (Model 1049C), WV-2 BuNo. 128323, was received at NAS Barbers Point by Airborne Early Warning (AEW) Squadron One (VW-1).
The Atlantic Barrier (BARLANT) consisted of 2 rotating squadron detachments sourced from AEW Squadron THIRTEEN (VW-13) and AEW Squadron FIFTEEN (VW-15) from NAS Patuxent River, Maryland and one squadron, AEW Squadron ELEVEN (VW-11), permanently based at Naval Station Argentia, Newfoundland. Their mission was to fly orbits to the Azores and back. There was an additional AEW Training Unit based at NAS Patuxent River for training flight crews and maintenance personnel.
BARLANT became operational on 1 July 1956 and flew continuous coverage until early 1965. The Barrier was shifted to cover the approaches between Greenland, Iceland and the United Kingdom (GIUK) barrier in June 1961. Aircraft from Argentia were staged through NAS Keflavik, Iceland, to extend coverage times.
The Pacific Barrier (BARPAC) received the first operational AEW squadron, Airborne Early Warning Squadron One (VW-1) and the first EC-121K aircraft. AEW Squadron Three followed with AEW Squadrons Twelve, Fourteen and Sixteen. In January 1958 VW-1 and VW-3 relocated to NAS Agana, Guam, M.I. where VW-1 continued its AEW commitments and VW-3 operational commitment was divided between AEW and Weather. BARPAC became ops with AEW Squadron TWELVE (VW-12) based at NAS Barbers Point, Hawaii, operating from a deployment  base at NAS Midway on 1 July 1958 and later expanded to include AEW Squadrons FOURTEEN (VW-14) and SIXTEEN (VW-16). Their orbits overlapped the radar picket stations of the ships of Escort Squadron Seven (CORTRON SEVEN), from roughly Adak Island to Midway. Normally 5 WV-2s/EC-121s were required at any single time to provide coverage over the entire line.
The Hawaiian Barrier force operations were discontinued by September 1965 and their EC-121K aircraft placed in storage. However, VW-1 continued operating until 1972 flying weather ops and supplying AEW to Naval forces in the Gulf of Tonkin. USN C-121, EC-121, WC-121 and NC-121 operations continued until 1975 in 7 other squadrons and until 1982 in an 8th. Some EC-121s were used in Vietnam, mirroring USAF EC-121 missions but orbiting the Gulf of Tonkin, as that was the USN's assigned area.
Fleet Air Reconnaissance Squadron ONE (VQ-1) and Fleet Air Reconnaissance Squadron TWO (VQ-2) operated EC-121M ELINT gathering aircraft at NAF Atsugi, Japan, and Naval Station Rota, Spain, respectively, until they transitioned to the EP-3B Orion and EP-3E Aries aircraft.
Weather Reconnaissance Squadron FOUR (VW-4) operated WV-3-cum-WC-121s between 1954 and 1975 as Hurricane Hunters, with its primary base at NAS Jacksonville, Florida and a forward base at Naval Station Roosevelt Roads, Puerto Rico. Its Pacific counterpart, Weather Reconnaissance Squadron Three (VW-3) Typhoon Trackers was the operational weather squadron in the Pacific, flying from NAS Agana, Guam, tracking typhoons from 1955 to 1960. On June 30, 1960 Weather Reconnaissance Squadron Three, VW-3, disbanded and many of its aircraft (8 - BuNo. 145 series) and crews were absorbed by VW-1, which retained AEW designation and took on the weather commitments and the Title of "Typhoon Trackers" of VW-3.  VW-4 later transitioned to  WP-3A Orion.
Also operating C-121 and EC-121 aircraft was Oceanographic Development Squadron EIGHT (VXN-8) at NAS Patuxent River, Maryland, which employed the aircraft for specific projects (e.g., Project BIRDSEYE, MAGNET, ASWEPS etc.) for the Office of Naval Rese
Lockheed EC-121 Warning Star