For a a brief period yesterday afternoon, United Airlines booking system was showing 0$ base fares +5$ in taxes on several routes. United shut down its booking system upon discovering the error. The mishap caught the attention of several mainstream media outlets including this USA today article, this one in Forbes, and this one from ABC. Below is a screen shot of kayak explore that I took this morning. The wide use of social media has meant that news like this can spread rapidly among the general public. It is unclear at this point if United will honor the fares.