2008.csv file is too large so it is not in my git repository. If you want to run the scripts then you may have to download the file from http://stat-computing.org/dataexpo/2009/the-data.html.
For this final project I will use 2008 flights data that I downloaded from http://stat-computing.org/dataexpo/2009/the-data.html. The file doesn't have the geographic coordination of each airport so I downloaded the file that contains the information of coordinates of each airport from https://gist.githubusercontent.com/tdreyno/4278655/raw/7b0762c09b519f40397e4c3e100b097d861f5588/airports.json.