The first gunship mentioned in the series was in Shadow, when a gunship was sent out to attack Liberator from Space City. This was presumably a space-going vessel, probably very short-range. Cally destroyed it with the neutron blasters.
The Federation force on Helotrix was equipped with gunships, and Hunda mentioned to Leitz that his 4th column had shot down two of them.
Justin told Dayna that the scientific personnel on Bucol-2, when leaving the planet towards the end of Intergalactic War, were shot down by an enemy - presumably alien - gunship minutes after take-off.