American Airlines Virtual

You can fly off network and submit a FREP.
No proof required.

As I stated earlier in a post. SIMACARS worked with MSFS2020 with FSUIPC7 loaded up. I made 3 test flights with it and there was no problem. I flew with the offline tab visible.
FSUIPC7 is a must.

Here is a test flight from KSEE to KMYF, 10 miles Start SIMACARS and use as always. You can see in the screenshot it registered as using SIMACARS for the comments, and kept a log in the SIMACARS folder.
I tried SIMACARS without FSUIPC, and this shows you need FSUIPC7 opened.