https://www.devex.com/people/usa-faq-what-days-are-frontier-flights-cheapest-know-2013710
https://hackmd.io/@James1998/rkqHBUVJ1l
https://www.devex.com/people/usa-faq-can-you-get-a-refund-from-turkish-airlines-2013420
https://community.more4apps.com/s/question/0D5P100000bb64kKAA/18667380738-does-frontier-ever-give-refunds-does-frontier-airlines-give-refund...
https://community.clover.com/questions/79857/americanairlines-what-day-is-cheapest-to-book-amer.html