I went back and took a look and I can't say that was a "crash". Worst 10 day period from Jul 4 2008 was -13% whereas the up move from Nov 2 peaked at +50%.When shale gas came online NG had a massive downtrend. Look at the monthly chart on tradingview for 2008/2009. Went from 13.5 to 2.5. The winter/summer spread April/May led to a hedgefund wipeout on several Billion dollar losses. It is called the widowmaker spread.
I'm not here to debate what is the definition of a crash. One person's crash is simply volatility for another. My point is NG tail moves are skewed to the upside. Especially at $3.
Could it crash to the downside? Sure, but just because it's possible doesn't make it probable.