In SG-1, does Earth have a unified defense fleet?

[Mr. Laser Beam]

Just a question about how the starships (i.e. the Prometheus and its ilk) operate in the Stargate universe.

I know the US Air Force has a few starships at its disposal, and that other countries do as well. They don't all operate as a single force, though, do they? Each ship is responsible to the government that owns and operates it, nothing more?

 

[Reverend]

It's been ages since I've really watched any of the shows, but if memory serves I think as of SGU it's kind of a NATO/UN type of arrangement.
The forces in question "belong" to their respective nations which lend them, their personnel and a certain amount of funds to Homeworld Command, which co-ordinates *all* of Earth's off-world operations under the oversight of the IOA, via the UN. One assumes there are all kinds of treaty stipulations about using alien technology on Earth and most especially about using them against other nations (short version: don't!) and no doubt all involved nations (including the US) are to some extent doing something sneaky under the table under the assumption everyone else is too.

 

[Romulan_spy]

In the beginning, it was just the US Air Force that had a starship (the USS Prometheus) operating in secrecy as part of the Stargate program. Then later, other countries like Russia, England and France were brought into the Stargate program. The US with the help of the other countries built many more ships, including the Daedalus class we see in Stargate Atlantis. Eventually, the IOA was formed, a multinational organization with civilian oversight over the Stargate program which would include all the starships.

 

[The Wormhole]

They never really went into detail on the matter, probably because only two of Earth's starships belonged to someone other than the US. But the Russian ship was destroyed in its first appearance and the Chinese ship was a throw-away line. And then, the times these ships are seen/mentioned they're involved in matters of galactic importance, eg the Russian ship was part of the task force assembled to try to prevent the Ori warships entering the galaxy, or a matter which concerns Earth's defense, like the Chinese ship was one of the Earth starships which tried to attack the Wraith hiveship headed to Earth in the Atlantis finale.

I imagine the ships probably are at the disposal of the governments of the countries they belong to, though when they IOA can also overrule and request the ships do their bidding too.