In the summer of 1971, Guam was chosen as a test vessel for Admiral Elmo Zumwalt's Sea Control Ship concept.
This ship was to operate a few VSTOL fighters and some ASW helicopters in order to free up supercarriers from convoy duty during a conflict with the Soviet Union.
 On 18 January 1972, she began extensive testing and in 1974 deployed in the Atlantic as a sea control ship with Marine Corps AV-8A Harrier VSTOL fighters and Sea King ASW helicopters.
Guam completed the SCS tests and reassumed her role as an Amphibious Assault Ship on 1 July 1974.
In October 1974 her aircraft complement, operated by the US Marine Corps, comprised six AV-8A, eight CH-46F Sea Knights, five CH-53D Sea Stallions and two Bell UH-1N Iroquis utility helicopters.

On 17 January 1977, in Barcelona, Spain, a landing craft being used as a liberty boat by USS Trenton and USS Guam, was run over by a freighter.
The Mike8 boat capsized and came to rest against the fleet landing pier.
Crewmembers from both vessels were on hand to assist with rescue operations.
There were over one hundred sailors and marines on board the landing craft.
49 sailors and marines were killed.
A memorial is erected at the landing pier in memory.
In the summer of 1971, Guam was chosen as a test vessel for Admiral Elmo Zumwalt's Sea Control Ship concept. This ship was to operate a few VSTOL fighters and some ASW helicopters in order to free up supercarriers from convoy duty during a conflict with the Soviet Union.  On 18 January 1972, she began extensive testing and in 1974 deployed in the Atlantic as a sea control ship with Marine Corps AV-8A Harrier VSTOL fighters and Sea King ASW helicopters. Guam completed the SCS tests and reassumed her role as an Amphibious Assault Ship on 1 July 1974. In October 1974 her aircraft complement, operated by the US Marine Corps, comprised six AV-8A, eight CH-46F Sea Knights, five CH-53D Sea Stallions and two Bell UH-1N Iroquis utility helicopters.
On 17 January 1977, in Barcelona, Spain, a landing craft being used as a liberty boat by USS Trenton and USS Guam, was run over by a freighter. The Mike8 boat capsized and came to rest against the fleet landing pier. Crewmembers from both vessels were on hand to assist with rescue operations. There were over one hundred sailors and marines on board the landing craft. 49 sailors and marines were killed. A memorial is erected at the landing pier in memory.
USS Guam (LPH-9)