Umberto,
KFLL uses scasm runway lights and it has been reported before:
This was confirmed by none other than yourself on post #5 on the second link.
senior moment?
KFLL does not use SCASM runway lights, which is a specific command to create a runway lighting system only, to be used together with a fully custom runway, which is known to have the side effect of making AI to disappear, and it has been used at Zurich ONLY.
However, KFLL uses SCASM PAPIs which might also cause the disappearing AI that might also be solved by turning AI shadows off, but it's not the same as in Zurich, it's a *different* FSX issue, which just happen to be fixed in the same way.
The involved file is KFLL_PAPI_SA.BGL. By removing this, the AI should reappear even with shadows on BUT, the PAPIs will look almost invisible then.