If I understand correctly: you have a CSV of all airports, including the lat-long coordinate. You can load this into QGIS as a "delimited text layer" and map it.

Then you need to edit it and add a new column, called something like "visited", and set this to "True" for all airports you've been to. Save your edits.

Then you use QGIS' layer styling to show visited airports with a red dot (or whatever) and non-visited airports with no symbol. You could do this by using a categorical symbol in the symbology dialog. You could also do this with a "Filter" on the layer.