WorldCorp, a charter airline company based at Dulles Airport, said it earned $5.2 million (37 cents a share) in the third quarter ending Sept. 30 as revenue more than doubled, to $40 million. The company reported a loss of $36.8 million during the same period last year because of operating losses and writeoffs associated with the discontinuation of its World Airways scheduled airline service in September 1986.

"This is the first quarter for which our results accurately reflect WorldCorp's earning power in its core business of contract flight operations," WorldCorp Chief Executive T. Coleman Andrews III said in a statement. WorldCorp, which owns World Airways and Key Airlines, provides worldwide contract air transport of passengers and cargo.

For the first nine months of the year, the company earned $671,000 (0 cents), compared with a loss of $28.6 million in the comparable year-ago period. Revenues were $104 million, compared with $41.9 million a year ago.

Radiation Systems Inc. of Washington said its earnings fell 29 percent, to $504,000 (9 cents), in the first quarter ending Sept. 30, compared with $710,000 (13 cents) a year earlier. The drop came as revenue rose 6 percent, to $9.3 million from $8.8 million.

Radiation Systems, which designs and makes antenna systems for satellite earth stations and other facilities, said the earnings and revenue for the quarter were "less than expected." It attributed the fall to precontract production charges associated with an upcoming sole-source contract that has not yet been awarded. The contract, which the firm did not identify, is expected to be let in the second quarter, it said.

United Financial Banking Cos. Inc. of Vienna reported earnings of $238,152 (27 cents) during the three months ending Sept. 30, down slightly from the $243,703 (27 cents) it earned during the same period last year.

For the first nine months of 1987, the company reported profits of $744,357 (84 cents), down 11 percent from $836,252 (98 cents) for the same period last year.

The decline was primarily a result of operating losses in the company's mortgage subsidiaries and higher income taxes under the new federal tax law, it said. The mortgage losses will not continue, as the company has decided to either discontinue or sharply curtail those operations, it said.

The company reported its total interest income for the quarter at $1.4 million, down from $1.7 million for the same quarter last year. Total interest income for the first nine months was $4.5 million, compared to $4.4 million for the same period last year. The banking company's assets were $65.9 million at the end of the first quarter, down from $86.4 million at the end of 1986.