To remove the static aircraft:
-Open the airport folder in the Community Folder.
-Open the scenery folder
-Change the static.bgl file name to static.bgl.bak
Example: Community\KDCA-drzewieckidesign-kdca\scenery\Washington National MSFS\KDCA_Static.BGL.BAK
This unfortunately does not make the gate usable, it just removes the static aircraft. If you are not using a “live” AI generator then no planes will park there and you will not be able to select the gate.