One view is that the SR-71 program was terminated due to Pentagon politics, and not because the aircraft had become obsolete, irrelevant, suffered maintenance problems or had unsustainable program costs. In the 1970s and early 1980s, SR-71 squadron and wing commanders were often promoted into higher positions as general officers within the USAF structure and the Pentagon. (In order to be selected into the SR-71 program in the first place, a pilot or navigator (RSO) had to be a top-quality USAF officer, so continuing career progression for members of this elite group was not surprising.) These generals were adept at communicating the value of the SR-71 to a USAF command staff and a Congress who often lacked a basic understanding of how the SR-71 worked and what it did. However, by the mid-1980s, these SR-71 generals all had retired, and a new generation of USAF generals wanted to cut the program's budget and spend its funding on new strategic bomber programs instead, especially the very expensive B-2 Spirit.