In October 1986, the USAF announced that operational Block 15 F-16A aircraft would be converted to air defence fighters for the Air National Guard, and would take over the fighter interception mission, providing the primary defence of North America against bombers and cruise missiles.

The F-16A/ADF (Air Defence Fighter) is based on the F-16A model.
The ADF conversion is centred primarily on upgrading the existing AN/APG-66 radar to improve small target detection and provide continuous-wave illumination (thus giving the ability to launch AIM-7 Sparrow BVR missiles). Further modifications include a night identification light in the port forward fuselage, advanced IFF, high frequency single side-band radio, improved ECCM and provision for GPS and AIM-120 AMRAAM missile datalink. The ADF F-16 can carry up to 6 AIM-7 Sparrow or AIM-9 Sidewinder missiles and retains the 20mm M61 cannon of the F-16A.

Distinguishing features of the ADF F-16A are the bulges on the fin/fuselage fairing and the searchlight on the port side of the nose. The bulges are caused by the relocation of the Bendix-King AN/ARC-200 high frequency single-sideband radio to the leading edge of the fin. This in turn caused the flight control accumulators, which were installed one over the other, to be relocated to either side of the tail fin. The bulges were installed to provide sufficient room for these accumulators.