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I'm not with Laminar Research, just a fellow simmer in the UK.
Just as an exercise, I loaded a flight in XP11.35 at Richard B. Russell airport (KRMG) and everything worked fine and no warning messages came up! Please see photo below.
Assuming that you already have all of the scenery files for the USA installed, I would simply suggest for now that you run the XP Installer app, as this will scan your files to see if any are missing, corrupt or are need of updating?
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