From what the Compendium has said as that most of the Earths government had come together to create the U.N. Spacy then you have other sub-branches of the U.N. such as the Air Force, Navy and Armed Forces.
Heres an excert from the Compendium:
1999
December
According to the first report of the ASS-1 study, the alien spaceship is determined to be a war vessel, and its alien crew to be giants whose height is five times that of Humans.
In preparation for alien warfare, a plan is drafted to unify the countries of Earth and to establish an Earth United Nations Government.
2000
March
Establishment of OTEC, an alien technology analysis research institute, through joint Japanese-American-Russian[soviet]-[West] German-English-French collaboration.
April
Research on anti-giant combat weaponry systems ([later designated as] Battroid and Destroid) begins.
The name U.N. Spacy has become an arguement to which its REAL name is derrivited from, to me, I like to call it the United Nations Space Agency, others have their own saying on what it is but also, its still an official meaning.
Here is another thing I caught eye of on the Compendium...
2007
January 20
Conclusion of United Nations Wars.
January
Training center for SDF-1 crew established on South Ataria Island.
February
The VF-X nontransformable flight test vehicle as well as the VF-X1 prototype variable fighter begins first flight tests.
Rollout of MBR-04-Mk I.
March
Stationing of Destroids aboard the SLV-111 Daedalus begins.
May
Construction on Grand Cannon V begins in the Brazilian Autonomous Region in South America.
June
Space tests of the VF-X1 begins.
November
Decision made to formally adopt the VF-X1. VF-1 series mass production begins.
Rollout of MBR-04-Mk IV [Mk III] Tomahawk.
2007-2008
Macross Zero
The United Nations government and Anti-United Nations forces secretly develop the VF-0 and SV-51 respectively while disputing over a recently discovered phenomenon on the island of Mayan in the South Pacific Ocean. (The events are kept secret for at least five decades.)
It says the VF-1 was mass produced earlier to the VF-0, which it states 2007-2008 for Macross Zero, but no approximate month, possibly late November of 2007?