Modern cycles (like 2410 or 2501) often use navigation specifications that FS9 cannot process. If you try to load a 2025 AIRAC into Microsoft Flight Simulator 2004, your FMS will crash or show "NAV DATA OUT OF DATE." Cycle 1708 acts as a bridge—it is recent enough to be structured similarly to modern data but old enough to work flawlessly on FS9 and 32-bit FSX.
Happy (and legal) flying.
X-Plane 12 requires a new navigation spec. Cycle 1708 will not work natively. Use the "XP12 Legacy Gateway" script to convert 1708's terminal procedures to XP12 format, but note that ILS frequencies will be offset. -FS9 FSX P3D X-Plane- Navigraph AIRAC Cycle 1708 Cheat