The A4D-4 was a 1958 proposal for a long-range all-weather attack version of the Skyhawk. It would be capable of delivering a nuclear weapon at low altitude. The wing shape was changed from that of a delta to that of a swept tapered shape. The span of the swept wing was increased by about 10 feet over that of the earlier A4D versions, which requred that the outer wing panels be provided with folding. Seven hardpoints were to be installed underneath the wing and fuselage. A larger bubble-shaped canopy was to be fitted.
The project never got past the preliminary design stage, since the Navy did not provide any funding.