Knight took closer to an hour to melt down than 30 seconds. NYSE and the SEC _chose_ not to reverse those trades but they could have. There are plenty of ways

Knight took closer to an hour to melt down than 30 seconds. NYSE and the SEC _chose_ not to reverse those trades but they could have. There are plenty of ways the exchange can undo those and also trade busts happen daily on every exchange. Almost certainly if a large index etf or fund lost everything to a software glitch the trades would be reversed and even if for policy reasons they weren’t they could be. The facility exists.