In November 2016 the first cross-border SAXFRA (Slovenian Austrian Cross Border Free Route Airspace “free route” airspace came into force. This airspace permits aircraft to employ flexible free routes without pre-defined ATS air routes. The omission of conventional air routes led Austro Control to the challenge of defining flight inspection profiles which until now are mapped against published ATS routes. To resolve this issue, FCS was tasked to carry out simulation studies with the aim of defining an optimized future flight inspection program. For this purpose, individual DVOR/DME navigational aids were examined with respect to their theoretical range. On this basis, an analysis of RNAV5 (B-RNAV) and RNAV1 (DME/DME) coverage in the SAXFRA area took place. This in turn will be used as the basis of the periodical flight inspections of Austrian en-route navigational aids in an efficient manner. Permanent reviews of flight inspection results are planned to further improve simulation parameters and to improve the quality of simulation results.