NEW YORK (TheStreet) -- Early Monday it seemed U.S. stocks would be able to shake off the negative news surrounding Greece. As the day went on the S&P 500 kept falling -- 496 stocks in the index closed lower on the day, drawing the index lower by 2.1% to start off the week. 

On CNBC's "Fast Money" TV show, Guy Adami, managing director of stockmonster.com, said the iShares Transportation ETF (IYT - Get Report) seems likely to decline to $137. Investors should consider buying Palo Alto Networks (PANW - Get Report) on a further decline and should scoop up the iShares China Large Cap ETF (FXI - Get Report) at $44. 

Tim Seymour, managing partner of Triogem Asset Management, looked more closely at Europe, saying German equities and European banks look to have more room on the downside. Specifically, he referred to UBS Group (UBS - Get Report) and Deutsche Bank (DB - Get Report) along with the iShares MSCI Spain Capped ETF (EWP - Get Report) and the iShares MSCI Italy Capped ETF (EWI - Get Report) as having more downside. 

With the CBOE Volatility Index (VIX.X) near $12 last week, Pete Najarian, co-founder of optionmonster.com and trademonster.com, continually said investors should buy it. However, now that it is near $19, up 34% alone on Monday, it doesn't seem like the time to buy. Given the current environment, though, things could get better for they get worse. 

Najarian is looking to buy the Health Care Select Sector SPDR ETF (XLV - Get Report) on a deeper decline. 

Steve Grasso, director of institutional sales at Stuart Frankel, said investors should not buy stocks if the S&P 500 breaks below 2,053, its 200-day moving average. 

Not everyone agreed. Rich Ross, managing director and head of technical analysis at Evercore ISI, said investors should buy on a drop below the 200-day moving average. Similar moves have happened just three times over the past three years and have ultimately led to strong gains. The fact that investors aren't fleeing to the U.S. dollar or gold also shows there's not a lot of fear surrounding the Greek situation, Ross explained. 

The strength of the euro seemed to catch investors off-guard, according to Dennis Gartman, editor and publisher of The Gartman Letter. If Greece leaves, which now appears to be the likely outcome, the euro should become stronger, he said. Gartman says it's unlikely that other struggling countries, like Spain and Portugal, will leave the eurozone because they have done a much better job at improving their economies. 

If Greece leaves the eurozone, the euro may have put in a low, Gartman concluded.

The conversation turned to airline stocks. Mark Dunkerley, president and CEO of Hawaiian Airlines (HA - Get Report), said the biggest drivers in the company's business remain favorable, that being oil prices and demand. Demand is "robust," he said, while oil prices remain significantly lower than one year ago. Capacities in Japan and China are also strong, while the overall industry continues to climb as well. 

The airlines look attractive but have been brutal for shareholders this year. Instead of buying now, Najarian said investors should wait until the week of July 20th, when many airlines will start reporting earnings. He expects the results to be "staggering" and perhaps shift investor sentiment for the sector. 

Stocks like Delta Air Lines (DAL - Get Report) and United Continental (UAL - Get Report) are currently trading near key support levels, Seymour said. While they are tempting to buy based on valuation, investors should steer clear if they break down. 

For their final trades, Seymour is selling the iShares Russell 2000 ETF (IWM - Get Report) and Grasso is a buyer of Tenet Healthcare (THC - Get Report). Najarian said to buy Bristol-Myers Squibb (BMY - Get Report) and Adami is buying Celgene (CELG - Get Report).

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This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.