It appears that Windows settings are now stored in "C:\Users\Stephen\AppData\Roaming\flightgear.org\FlightGear\flightgear.ini". I did not see any airport settings in this file. (a copy of the file is displayed below) I ran a file search and was unable to find a source file for setting an airport. I also added KRMH under "settings" -> "additional settings". While that added KRMH to the "tools" -> "view command line", FlightGear still booted into LKPR.
I was unable to find "preferences.xml" that is supposed to be located in: "C:\Documents and Settings\{Your username}\Application Data\flightgear.org\", Possibly this reference was not updated to reflect the Window's revision from XP to Windows 10.
[General]
restore-defaults-on-run=true
aircraft-cache="Text Deleted for this posting"
ratings-filter=true
only-show-installed=false
recent-aircraft=@Invalid()
recent-location-sets=@Invalid()
window-geometry=@ByteArray(\x1\xd9\xd0\xcb\0\x2\0\0\0\0\x2*\0\0\0\xa5\0\0\x5\xa2\0\0\x3]\0\0\x2\x32\0\0\0\xc4\0\0\x5\x9a\0\0\x3U\0\0\0\0\0\0\0\0\a\x80)
extra-args=
[mpSettings]
mp-server=
enableMP=false
callSign=
mpCustomServer=
[timeSettings]
customTime=@DateTime(\0\0\0\x10\0\0\0\0\0\0%hY\0\0\0\0\0)
customTimeIsGMT=false
[weatherSettings]
fetchMetar=true
customMETAR=
[generalSettings]
startPaused=false
autoCoordination=false
showConsoleWin=false
[downloadSettings]
terrasync=false
downloadDir=
[viewSettings]
fullscreen=false