One step that would make it easier is to encapsulate your code in a class rather than using global variables. As it is right now, everything leans on that "droppedFile" global getting set, and the only options are to pull from the command line argument or change the statically coded value which makes your code pretty hard to import.
If you can organize your code such fw2kml is a class that can be imported into other scripts, that would help for making a GUI. You'd have something like:
Python:
class fw2kml():
def __init__():
pass # do anything to set up the conversion tool
def convertFile(droppedFile):
totalflights = 1
badtimedelta = False
# pretty much copy paste your entire try/except block in here
tool = fw2kml()
if len(sys.argv) > 1:
for path in sys.argv[1:]:
tool.convertFile(path)
# allows you to do ./fw2kml.py file1.csv file2.csv ...
I can't do much right now because I'm at work, but I can take a look later and make some changes with a pull release for you if you're okay with that.