Washington-based USAir Group Inc. yesterday reported first-quarter earnings of $10 million, 45.9 percent less than the company's profits of $18.5 million in the first quarter of 1984.

Earnings per common share for the quarter were 41 cents, compared with 77 cents for the same period last year.

"Results were better than anticipated in light of widespread use of promotional fares during the period," said Edwin I. Colodny, chairman and president of USAir Group.

The airline's sales for the quarter were $394.5 million, versus $372.2 million in the year-ago period.

Ethyl Corp., a chemicals company based in Richmond, earned $28.2 million (43 cents) in the first quarter, 14 percent more than the $24.7 million (30 cents) in profits for the same period in 1984.

Ethyl's net sales for the period were $377.4 million, a 10 percent drop from $418.1 million a year earlier.

The company's earnings were hurt by a decline in demand for lead and other antiknock additives used in gasolines, according to Ethyl Chairman Floyd D. Gottwald Jr.

Sovran Financial Corp.'s earnings were up 16.5 percent for the quarter, based on a net income of $21.2 million ($1.19) over $18.2 million ($1.08) in the comparable 1984 period.

"Net income benefited from an increase in net interest income, resulting primarily from significant growth in the average volume of loans," said Sovran Board Chairman C. A. Cutchins III.

United Virginia Bankshares Inc. reported a 23 percent increase in its first-quarter profits, with its earnings rising to $15.4 million ($1.23) from $12.6 million ($1.03) for the same period a year ago.

UVB Chairman Joseph A. Jennings attributed the increased profitability to higher noninterest operating income and strong loan growth.

Its average loans increased by 16 percent to $4.4 billion from $3.8 billion between the first three months of 1984 and the first three months of 1985. The highest dollar gain was in commercial loans, which grew by $434 million, or 21 percent, to $2.6 billion.

The increased profits came despite an increase in nonperforming assets. As of March 31, these tallied $38 million -- $5 million higher than a year earlier and $9 million higher than the end of 1984.

The bank increased its provision for loan losses to $5.6 million, up from $2.6 million for the same period a year ago but equal to the $5.6 million provided for at the end of 1984.

United Bancorp of Maryland Inc. posted a 32 percent increase in profits for its first quarter to $178,927 ($1.06) from $135,687 (97 cents) during the first three months of 1984.

Assets rose by 28 percent to $83.3 million while deposits were up by 27 percent to $75 million.

Central National Bank of Maryland's earnings climbed 28.3 percent during its first quarter, from $250,000 (41 cents) for the same time period a year ago to $321,000 (47 cents) this year. The bank attributed the increase to a higher level of earning assets, which rose by 13.8 percent from $97.2 million to $110.6 million, as well as improved interest margins and additional capital. The bank rasied $1.2 million in capital in April 1984.