Winter storm Stella grounded more than 5,000 flights on Monday and Tuesday, which has taken a toll on an already-struggling airline industry.

United Continental Holdings Inc. (UAL) and Delta Air Lines Inc. (DAL) fell 7.5% and 2.5% over the past week, respectively. The U.S. Global Jets ETF (JETS) – which tracks the larger airline and parts industries – fell around 2.85% over the past week.

The industry has already been struggling with struggling unit revenue that led Delta, American Airlines, and Southwest Airlines to lower their forecasts for the first quarter of 2017. Rising fuel costs and adverse weather conditions were two of the causes cited by the airlines in their downgrades. Labor costs are also on the rise as unions negotiate new deals at higher costs while the revised travel ban announced by president Trump could hurt revenue.

Despite these concerns, Warren Buffett has been an avid buyer of American Airlines Inc. (AAL), Delta, Southwest Airlines Inc. (LUV), and United Continental. The billionaire investor is betting that the consolidation since 2005 will help control costs and avoid trade wars, while improving metrics like passenger revenue per available seat mile (“PRASM”) over the long-term.

On a technical level, United Continental could see significant support at around $61.50 and its 200-day moving average at $58.77. The Moving Average Convergence Divergence (MACD) remains in a bearish downtrend, but the Relative Strength Index (RSI) stands at highly oversold levels at 34.08. Traders should watch for a rebound from trend line support to re-test its highs of around $75.00 to $77.50 or a breakdown below these support levels.

Delta Airlines could similarly see support at its 200-day moving average at 43.04 or trend line support at around $42.00. Looking at technical indicators, the RSI appears oversold at 39.58 but the MACD remains in a long-term bearish downtrend.

Traders should watch airlines stocks for a rebound or breakdown from these key upcoming support trend lines. With the winter storm ending, airlines are likely to see a rebound from oversold conditions, but the long-term picture remains a little more cloudy.

Stock charts courtesy of StockCharts.com. Author holds positions in stocks mentioned via mutual funds and ETFs.

Want to learn how to invest?

Get a free 10 week email series that will teach you how to start investing.

Delivered twice a week, straight to your inbox.