Below is an essay exploring the importance of software serial numbers, using Realflight 9.5 as a primary case study.
On some versions, it is printed on a sticker on the back of the InterLink DX controller.
If you bought a boxed copy of RealFlight 9.5:
Check your email receipt or the download page from the storefront where you bought the software (e.g., Tower Hobbies or Horizon Hobby).

