File Description: A definition of the navdata data files including
wpNavAID.txt, wpNavAPT.txt, wpNavRTE.txt and wpNavFIX
used by all PMDG FMS-equipped aircraft. Although
this file is currently available from Navigraph,
the format of this file predates their service
and is not proprietary information.
Understanding the layout of these files will make
it easier to add custom airports.