Norfolk Southern Corp.'s (NSC) first-quarter net income dropped 39% amid a drop in traffic volume and a decline in once-reliable coal revenue.

Following the results, which missed analysts' estimates, shares of the largely East Coast rail company fell 10% to $33.57 in after-hours trading. Norfolk's stock has lost over half its value from September.

Norfolk had maintained profitability during the downturn on the strength of its coal-shipping revenue, but rival CSX Corp. (CSX) reported last week its first-quarter earnings dropped 30% as coal volumes dropped.

The freight sector has been under pressure as the economic downturn has hurt demand for nearly all goods, and the weakness in coal shipping in this quarter showed the industry's woes have spread to its best performer by volume in recent quarters. Norfolk didn't break out its volume results by segment, but joined CSX in seeing weakness in coal shipping.

The company reported net income of $177 million, or 47 cents a share, down from $291 million, or 76 cents a share, a year earlier.

Revenue dropped 22% to $1.94 billion, amid a 20% drop in traffic volume and lower fuel-related revenues.

Analysts polled by Thomson Reuters expected per-share earnings of 55 cents on revenue of $2.04 billion.

Revenue from coal shipping fell 9%. For general merchandise, revenue decreased 28%, as intermodal revenue, or sales from the movement of freight by two or more modes of transportation, fell 25%.

Chief Executive Wick Moorman said the company has responded to the poor economic conditions by aggressively controlling costs, but said enhancements in service and projects would better position the company for the economy's eventual recovery.

-By John Kell, Dow Jones Newswires, 201-938-5285, john.kell@dowjones.com