Introduction  Area Navigation (RNAV) systems, aeronautical applications,  and functions that depend on databases are widespread.  [Figure 6-1] Since the 1970s, installed flight systems  have relied on airborne navigation databases to support  their intended functions, such as navigation data used  to facilitate the presentation of flight information to the  flight crew and understanding and better visualization  of the governing aeronautical flight charts. With the  overwhelming upgrades to navigation systems and fully  integrated flight management systems (FMS) that are now  installed in almost all corporate and commercial aircraft,  the need for reliable and consistent airborne navigation  databases is more important than ever.  Chapter 6$_{ }$ Airborne Navigation Databases 