NEW YORK (TheStreet) -- Shares of Delta Air Lines  (DAL) - Get Report are falling 4.26% to $33.71 on heavy trading volume Monday afternoon as concerns about the airline operator's exposure to the U.K. market mount following Britain's decision on Friday to exit the European Union. 

The International Air Transport Association warned of a "permanent downward shift" between 3% and 5% in U.K. passenger volumes by 2020 due to the "Brexit" vote, Deutsche Bank pointed out in a note cited by Barron's. 

"While we continue to believe that London will remain a major [Origin & Destination] market for the foreseeable future, the vote to leave the EU does create uncertainty with respect to near-term demand for air travel to/from the UK as well as how the UK will feature in a revised EU - US Open Skies accord," the firm stated.

The U.K. market for 2016 represents 2.8% of Delta's capacity, indicating potential downside risk to per-share earnings, Deutsche Bank added. 

The firm maintained its "hold" rating on shares. 

About 18.04 million shares of Delta have been traded so far today, well above its average trading volume of roughly 10.69 million shares per day. 

Separately, TheStreet Ratings team rates the stock as a "buy" with a ratings score of B.

Delta Air Lines' strengths such as its impressive record of earnings per share growth, compelling growth in net income, largely solid financial position with reasonable debt levels by most measures and notable return on equity. We feel its strengths outweigh the fact that the company shows weak operating cash flow.

You can view the full analysis from the report here: DAL

TheStreet Ratings objectively rated this stock according to its "risk-adjusted" total return prospect over a 12-month investment horizon. Not based on the news in any given day, the rating may differ from Jim Cramer's view or that of this article's author. 

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