https://www.studocu.com/en-us/messages/question/13158050/what-day-of-the-week-is-american-airlines-the-cheapestthe-cheapest-day-to-buy-%F0%9D%98%88%F0%9D%98%AE%F0%9D%98%A6%F0%9D%98%B3%F0%9D%98%AA%F0%9D%98%A4%F0%9D%98%A2%F0%9D%98%AF-%F0%9D%90%80ir-lines