[3] The Army had initiated the Advanced Aerial Fire Support System (AAFSS) program to develop the Lockheed AH-56 Cheyenne for the anti-tank gunship role, but development of the Cheyenne did not go smoothly, and as one writer put it, "the vultures began to gather", with Sikorsky and Bell trying to sell unsolicited alternatives to the Army.

The Sikorsky offering was the S-67 Blackhawk, a sleek gunship, which despite the name had no real relation to the later UH-60 Black Hawk utility transport helicopter.

Two prototypes were built, one with a P&WC T400-CP-400 Twin Pac dual turboshaft engine system much like that used on the AH-1J, but with a stronger drivetrain allowing operation at full 1,800 shp (1,340 kW) power, and the other with a single Lycoming T55-L-7C turboshaft engine rated at 2,000 shp (1,490 kW).

It looked much like an AH-1J, except for a longer and distinctive "buzzard beak" nose and a ventral fin like that on the original Model 209 demonstrator.

All the gunner had to do was keep the target in his sight, and the missile fire control system adjusted its flight appropriately.

Both the gunner and the pilot had Sperry Univac helmet-mounted sights to allow them to acquire targets for the KingCobra's missiles and gun.

[3] A long-span "big wing", 13 feet (4.0 m) wide, was designed for the KingCobra, but apparently never fitted except as a static mockup.