I have looked at your .skp file a bit.
I also exported a .dae. I used the latest dev release of MCX to put it in FSX SP2.
You do have some faces reversed at various locations around your terminal.
IMO the easiest way to see the reversed faces in Sketchup is to edit the Styles->Face Settings and change the Back Color to a distintive color that you are unlikely to mix up with some part of a project.
In SU 2017 I have the default tray showing and that is why the screenshot looks like this:
View attachment 79188
If your version of SU doesn't have this tray, you will have to find where the styles are.
You can make this setting part of your default startup file by opening SU, make whatever changes you want and then use the File->Save As Template. Make sure the CheckBox for set as default template is checked.
FWIW and with all due respect:
I see some unrelated nit-pick problems on the street side of the terminal.
The entrance doors. You have them with transparency, but the brick texture goes behind them. In the sim I see Z-fighting on that and the glass texture to the right of it.
Two of the white framed windows. The one furthest to the left and the one to the right of the entrance doors are not aligned with the rest of the window.
The ramp side of the terminal:
Check the two big windows. There appears to be alignment or location problems with both of them. On the one to the left of the jetway, I see Z-fighting in the sim.
I imagine that you have spent enough time working on this that it has got to the point where it is easy to overlook nit-picky details.
If you have made this for your own use only, you may not care.