Warning, my post is as spoiler filled as it gets today...
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Actually, all those ships, in the show, were built by the USAF. The X-302's were based of the death glider design - but are designed with thier own hyperspace drives, and the X-303 was an original build. There are several episodes covering the X-303's exploits.
Stargate Atlantis is based entirely off-world in another galaxy. There is a lot more information at
http://www.gateworld.net/atlantis/index.shtml