article_snippet.sent: A flash crash is a sudden plunge in stock prices.
article_snippet.sent: On May 6, 2010, the US stock market dramatically collapsed – wiping billions off the world's biggest companies.
article_snippet.sent: But, by 3.07pm, the US stock market had miraculously regained most of the 600-point drop – making the Flash Crash the second-largest point swing ever recorded.
article_snippet.sent: Hours later, European markets opened and crashed in similar fashion.
article_snippet.sent: The cause of A flash crash puzzled US officials.
article_snippet.sent: Theories included technical glitches, high frequency trading or changes in market structure – but never criminal activity.
article_snippet.sent: Theories allegedly used automated trading software to 'spoof' the US stock market by placing up to 19,000 orders and then cancelling up to 19,000 orders, all in under one second.
article_snippet.sent: However, manipulation wasn't identified as The cause of the crash in a September 2010 report, suggesting that regulators did not see Theories activity at that time.