sed 1d 2016.csv > 16.csv
sed 1d 2017.csv > 17.csv
sed 1d 2018.csv > 18.csv
sed 1d 2019.csv > 19.csv
sed 1d 2020.csv > 20.csv
sed 1d 2021.csv > 21.csv
cp 2015.csv flights.csv
cat 16.csv >> flights.csv
cat 17.csv >> flights.csv
cat 18.csv >> flights.csv
cat 19.csv >> flights.csv
cat 20.csv >> flights.csv
cat 21.csv >> flights.csv