Dart Drug Corp. yesterday reported record earnings of $3.6 million ($2.04 a share) for its fiscal year ended Jan. 31, and Chessie System Inc. reported record first-quarter earnings of $20.3 million ($1.01).

Dart said its full-year record earnings compared with $2.5 million ($1.35) for the previous fiscal year and that sales increased from $208.6 million to $231.2 million.

Fourth-quarter net income increased from $787,000 (43 cents) or $1.3 million (73 cents) as sales grew from $60.1 million to $66.97 million.

Tightened expense controls and aggressive merchandising policies contributed to the record earnings, according to Dart President Hebert H. Haft.

Chessie's record first-quarter earnings compare with 1979 first-quarter earnings of $9.3 million (47 cents) and the previous first-quarter record of $16.1 million (87 cents) set in 1979. The year-to-year increase was 118 percent.

Railway operating revenues of $471.6 million compare with a year-ago total of $399.7 million.

Chessie Chairman Hays T. Watkins characterized the results as excellent and said they were generated "mainly by an exceptionally high volume of coal traffic -- especially for overseas export, a reasonably mild winter, good performance by our nonrail subsidiaries and management's continuing cost-control efforts."

Revenues from transporting coal, coke and iron rose 36 percent from a year ago to $174 million, and merchandise traffic revenues rose 11 percent to $269 million. Loading at Chessie's Baltimore and Newport News export terminals were 55 percent greater than during the first quarter of 1979.

Watkins also noted that financing $26 million of locomotive purchases and retiring $14 million of bonded debt from internal sources reduced cash and working capital balances. But he said the company will save money on interest expenses.

D.C. Trading and Development Co. earnings for 1979 were $2.2 million (90 cents a share), 20 percent higher than 1978 earnings of $1.8 million (75 cents), according to O. Roy Chalk, chairman of the company which formerly was named D.C. Transit System Inc. Neither revenues for the year nor any fourth-quarter results were given.

Maryland Realty Trust said yesterday that it lost $130,800 in its first quarter ended Feb. 29 compared with a $57,000 loss a year earlier. Revenues fell to $350,700 from $388,234.