That's the best price we could find for select routes by $9. Buy Now at DealBase Tips On the DealBase landing page, click "United Airlines" in the top line to see this sale. We found this price on flights departing on January 7 from Boston, MA (BOS) to Washington, D.C. (IAD). All prices, dates, and booking details were valid at the time of publication. Book this travel deal by the end of the day for flights from December 17 through March 4.