Alert fighters
From Battlestar Wiki, the free, open content Battlestar Galactica encyclopedia and episode guide
Alert Fighters are group of Vipers "standing by" within a battlestar's launch tubes with their pilots in or very near their cockpits in preparation for a quick launch.
The purpose of Alert Fighters are to support a Combat Air Patrol with the intercept or elimination of any incoming enemy threat.
Notes
The official definition taken from the Official Battlestar Galactica Magazine #3 is 'A rotating group of Colonial Vipers which are constantly ready for immediate launch. Their function is to act as support from the Combat Air Patrol.'