Sixth-millennium starfighters are obsolete spacecraft that the Proteus enforcers use to patrol and defend Proteus. Croad is the enforcer that is shown piloting such a craft (The Long Patrol).
Notes
Although apparently 1,000 yahrens older, the design of the sixth-millennium starfighter is extremely similar to that of the Colonial Viper. The sixth-millennium starfighter is much more squat over all and has two engines rather than three.