At the beginning of 1970, USMC units at Da Nang AB included VMCJ-1, VMF (AW)-225, VMF (AW)-242 and VMFA-542. In late January 1970 as part of Operation Keystone Bluejay VMFA-542 departed Vietnam and VMO-2 moved to the base from Marble Mountain Air Facility. In July–August as part of Operation Keystone Robin Alpha, VMCJ-1 and VMF (AW)-242 departed Vietnam while the withdrawal of Marine Aircraft Group 13 from Chu Lai Air Base saw the relocation of VMFA-115 and VMA-311 to Da Nang AB as part of MAG-11. During 1970 Marine engineers constructed 170 "Wonderarch" concrete and steel aircraft protection shelters at Da Nang AB and Marble Mountain Air Facility.