The P-51 used the NACA 45-100 which was supposed to be a laminar airfoil but never achieved that status due to manufacturing tolerances. Was not a symmetrical airfoil.
From a NASA report
One of the major emphases of the documentary record is the experience of the North American P-51 Mustang, one of history’s most remarkable airplanes and the first aircraft to employ a NACA laminar-flow airfoil. More than any other case study, the Mustang’s performance in the war demonstrates how the NACA’s laminar-flow airfoils proved to be a success, despite also being a failure. The record of this magnificent fighter plane confirmed expectations of appreciable improvements in speed and range as a result of the low-drag design, but practical experience with this and other aircraft using advanced NACA sections in the 1940s also showed that the airfoil did not perform as spectacularly in flight as in the laboratory. Manufacturing tolerances were off far enough, and maintenance of wing surfaces in the field were careless enough, that some significant points of aerodynamic similarity between the operational airfoil and the accurate, highly polished, and smooth test model were lost. Because the percentage drag effect of even minor wing surface roughness (e.g., dirt, dead bugs, and the dusty footprints of airplane crewmen) increased as airfoils became more efficient, laminar flow could be maintained in actual flight operation only in a very small region near the leading edge of the wing.
Still, the Mustang’s airfoil section turned into an excellent wing. Ironically, this development was due to its high-speed performance rather than its low-drag. In “one of those rare instances in the history of technology in which a system becomes a success because it unexpectedly excels at something for which it was not originally designed,” a decade of dedicated airfoil research by the NACA resulted, not in what Eastman Jacobs and his colleagues were after, but in something else, almost as good.27 Not only were the NACA’s 6-series laminar-flow airfoils used with great success on the Mustang, they were also to be employed on just about every other high-speed airplane that came after it, up to the time that sophisticated computer-aided design took over and started customizing advanced airfoil shapes in the 1980s.