The Cooper vane—the modification mandated by the FAA after the hijacking—addressed the problem directly. The device, installed at the base of the airstair, was designed so that the stair could not be deployed while the aircraft’s engines were running and the plane was in motion. It made the specific method Cooper used physically impossible on aircraft equipped with the modification.
The vane was named for the case that prompted its creation. It is one of the case’s more peculiar legacies: a piece of aviation safety equipment named after an unknown man whose real name is still unknown.
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## Everything That Has Been Tried
It is worth being explicit about the scale of the investigative effort in the Cooper case, because it provides important context for understanding why the case remains unsolved.
The FBI’s investigation produced a 66-volume case file. The bureau examined more than 800 possible suspects in the first five years alone. By the case’s later years, the number of serious suspects processed had exceeded 1,000. Each of these candidates required investigation: background checks, interviews, physical description comparisons, alibi verification, and in some cases more extensive investigation.
The FBI deployed the behavioral science methods that were at the frontier of criminal profiling in the 1970s. The bureau used aerial photographic technology—the SR-71—that was ordinarily reserved for military intelligence purposes. It conducted ground searches with military personnel and organized extensive volunteer efforts.
Laboratory analysis of the physical evidence has advanced with the available technology over fifty years. The tie was analyzed for DNA when DNA profiling became applicable to forensic cases. The particle analysis of the tie’s microenvironment reflects research methods that were not available in 1971 or for many years after. The diatom study of the Tena Bar bills applied a scientific methodology that required a level of specificity about environmental markers that was not part of the 1971 or even the 1990 forensic toolkit.