Early panel codes were developed in the late 1960s to early 1970s.  Advanced panel codes, such as Panair (developed by Boeing), were first introduced in the late 1970s, and gained popularity as computing speed increased.  Over time, panel codes were replaced with higher order panel methods and subsequently CFD (Computational Fluid Dynamics).  However, panel codes are still used for preliminary aerodynamic analysis as the time required for an analysis run is significantly less due to a decreased number of elements.