I think I may have solved it.
I tried a number of things including removing the community folder, re-starting the sim, exiting and restoring the community folder to no avail.
I began poking around other MSFS folders and came across one called 'SceneryIndexes.' I noticed many files with very recent timestamps and other with older timestamps. Searching through some of the dat files I found references to the two airports, even though they weren't installed anymore. On a whim I moved this folder out to the Desktop and started MSFS, hoping it would re-initialize these scenery indexes. Boot was slower than normal (which is pretty slow...) but that did the trick. After I reinstalled the add-on airports they re-appeared. Hopefully I didn't do any lasting damage
- dcc