The purpose of this paper is to describe formats developed for transmitting aviation-related messages over the Discrete Address Beacon System (DABS) data link. Initial data link applications include: (1) Minimum Safe Altitude Warning (MSAW) alerts (Terminal Area) (2) Takeoff Clearance Confirmation (3) Altitude Assignment Clearance Confirmation (Enroute) (4) Weather Reports (a) Surface Observations (b) Terminal Forecasts (c) Pilot Reports (d) Winds Aloft (e) Hazardous Weather Advisories (f) Digitized Weather Radar Maps (5) Enhanced terminal Information Service (ETIS) (6) Downlink of Airborne Measurements. The formats described in this paper cover the DABS communications formats for uplink messages from the DABS sensor to the airborne data link system, and the downlink messages from the aircraft. Downlink messages include pilot requests for routine weather information and ETIS service, pilot acknowledgements for uplink tactical messages, and airborne measurements.