Jara, no go. Just tried the static planes only option and this is the message I'm getting. I thought I have all the correct mods installed? Here's the list of the mods.
Mea culpa, Fullofit.
You are right, there was a bug in the code.
Fixed version, WOFF UE Mission Editor 1.5.6 is available here
1) Fixed bug in Populate Airfields method causing false warning "Realistically populated airfields mod not installed", thx to Fullofit for pointing it out