To many investors, the stock market’s flash crash of May 6, 2010, when the Dow Jones Industrial Average plunged 600 points in about five minutes, is now ancient history.

But not to David Lauer, a high-frequency trading consultant for Better Markets, a Wall Street reform group.

“It is simply a matter of time before we have another catastrophe of the same magnitude or worse than the flash crash,” he said in prepared testimony for the Senate Banking Committee, CNBC reports. “The next time it happens, we may not be so fortunate with regard to the timing.”

Editor's Note: The ‘Unthinkable’ Could Happen — Wall Street Journal. Prepare for Meltdown

The crash occurred around 2:45 p.m. EDT, long after the close of European markets, but sill more than an hour ahead of the 4 p.m. U.S. close.

“It was only luck that the flash crash didn’t start in the morning, inciting markets around the world to crash, or at 3:45 p.m. EDT, with the market closing after the drop, but before it could recover,” Lauer said.

“If this were to happen, there would be an overnight exodus from the market with disastrous consequences for the U.S. economy.”

New York Stock Exchange floor broker Doreen Mogavero sees weak regulation as the problem.

“High-frequency trading, while not in itself a problem, is one aspect of a marketplace in which officials have opted to regulate in favor of speed rather than to concentrate on the stability of pricing that draws the investor to the market,” she told The New York Times.

Editor's Note: The ‘Unthinkable’ Could Happen — Wall Street Journal. Prepare for Meltdown