Intriguing flight files in STEAM mission

I recently acquired the latest mission pack from STEAM, "Arctic Rescue" (20 missions). When looking at them I found that the flight (.FLT) files were "compiled/coded" and totally unreadable. This is something I've never seen before.

However, if you run a mission and save it, the resulting flight file is normal!

Has anyone seen this kind of flight file before?

Cheers,

eskil