Thanks again, Dick.
IIUC, Airport2Project_1_0_0_20 does not interpret an Airport Boundary / Background Polygon in your HGLH project attached above.
Can you create an 'airport flatten' at HGLH ...so we can use BGLViewer to see where / how SU9 codes Airport Boundary "Flatten" Polygons ?
Thanks in advance for sharing any additional insights you may have regarding this aspect of the SU9 et seq. updated coding.
Just a heads up on my post regarding Airport2Project_1_0_0_20 functionality ...that I posted in the BGLViewer thread.