In the science fiction television series Stargate SG-1 and its sequels, several types of starships are introduced in the later seasons. In the series, they are the product of several years' worth of research into alien technologies discovered on off-world missions to other planets visited via the stargate. The stargate is an alien device discovered on Earth that allows near instantaneous travel to other planets via a controlled wormhole across a network of similar gates. The stargate was created by an extinct race called the Ancients, but are in use by aliens, some of which use both stargate and starship travel. Some of these alien races are hostile to Earth and bent on galaxy-wide domination, so Earth starships are built by the US military through billions of dollars in secret funding to respond to the threat.
After several prototype models, including some failures, Earth begins constructing its own space-capable fighters and larger, mothership-style vessels. The primary source of inspiration for the early models is scavenged Goa'uld technology, which is later replaced with entirely Earth-made components as they gain the expertise to fabricate the materials. The plans for these vessels are shared with the Russians as part of the deal to use their Stargate.
The first successful ship fielded by Earth is the F-302, a small, two-man craft somewhat similar to a traditional human fighter aircraft, but capable of spaceflight and interstellar travel. F-302s are the standard dogfighting attacker used by the Stargate Program. Later on, Earth begins creating interstellar battlecruisers, the first of which is the Prometheus. While the F-302 is generally a match for a Goa'uld Death Glider (and in some ways is superior), Earth battlecruisers are at first inferior to the equivalent vessels of other races. In the SG-1 finale, "Unending", the Asgard provide Earth with technology that closes this gap, making Earth ships some of the most powerful vessels in the series.
The X-301 fighter-interceptor is Earth's first attempt at building a fighter capable of space travel and orbital defense against the Goa'uld. It is featured in the episode "Tangent". The X-301 is constructed in Area 51 from a combination of Earth components and parts salvaged from two Goa'uld death gliders from the Apophis motherships. The X-301 is equipped with a Goa'uld inertial propulsion system capable of nullifying any g-force on pilot, stealth technology that hides it from radar, and two naqahdah-enhanced AIM-120 AMRAAM air-to-air missiles. It was mentioned that they would be effective against the Goa'uld Motherships if armed with shield modulators, however, no missiles fired by Earth ships were ever seen to penetrate through Goa'uld shields, so they may never have had that form of technology (working), and it was only mentioned in reference to the X-301, not the 302.