March wasn't the best month for the S&P 500, with the index dropping 5.8%. It was a tough month all around, as 98 of the S&P 500 stocks finished the month down at least 10%, but two especially had a bad month: Delta Air Lines (DAL -0.29%) and United Airlines (UAL 0.36%). Delta and United were the S&P 500's worst-performing stocks in March, falling 27.5% and 26.4%, respectively.

^SPX data by YCharts

Why did both airlines have such a bad March?

Broader economic uncertainty took its toll on both companies, but there were also industry-specific problems that caused the stock price drops. Delta lowered its revenue growth guidance from 6%-8% down to 5% (at the higher end). It also cut its earnings-per-share (EPS) guidance from $0.70 to $1 down to $0.30 to $0.50.

United also lowered its guidance as it projects its revenue will take a hit. It noted a slowdown in corporate and government travel, especially as the federal government focuses on reducing its spending. United says government-related booking decreased by half.

As new tariff plans go into effect and concerns about inflation and a potential recession ramp up, both companies could face some near-term troubles as consumers, companies, and governments cut back on travel. It will take time to see how it all plays out, but investors should expect volatility to continue along with potential drops.

As of market closing on April 11, Delta's and United's stocks are down 30.8% and 31.3% for the year, respectively.