News first spread through the FlyerTalk forum, eventually leaking onto Twitter, before United caught on. We happened to step away from the internet for a brief period to have lunch, and our window to attempt to book a mistake fare had already passed. That's just how quickly the deal came and went.
There's no official statement yet from United, and no word on whether or not the airline will honor the tickets successfully booked for the incorrect price.
The last such rush on a mistake airfare happened around this time last year, when El Al tickets to Israel from the US dropped as low as $350 roundtrip, which the airline actually honored.
UPDATE 4pm EST September 13: The official @United twitter account has confirmed that the mistake fares will be honored for those who successfully booked tickets. Proof:
We’ve reviewed the error that occurred yesterday and based on these specific circumstances, we will honor the tickets.— United (@united) September 13, 2013