With the failure of the CIA's Project Rainbow to reduce the radar cross-section (RCS) of the U-2, preliminary work began inside Lockheed in late 1957 to develop a follow-on aircraft to overfly the Soviet Union. Designer Kelly Johnson said, "In April 1958 I recall having long discussions with Deputy Director for Plans Richard Bissell over the subject of whether there should be a follow-on to the U-2 aircraft. We agreed ... that there should be one more round before satellites would make aircraft reconnaissance obsolete for covert reconnaissance."