USAF officials had originally intended the conversion to be a relatively straightforward matter of removing the carrier-specific features and fitting USAF avionics, but otherwise adhering as closely as possible to the original A-3 design. For this reason, no prototypes were ordered when the USAF issued its contract to Douglas in June 1952, instead having opted for five pre-production "RB-66A" models to be supplied, the aerial reconnaissance mission being considered to be a high priority for the type. However, this contract would be amended, involving multiple new variants that were added and swapped about. Likewise, the list of modifications sought quickly expanded; to meet the changing requirements, the supposedly easy conversion would become what was essentially an entirely new aircraft.