Business highlights

New York-based Citicorp and the Chase Manhattan Bank are interested in buying or merging with some of Maryland's troubled thirfts, according to press reports. State officials confirm discussions with out-of-state banks. Meanwhile, with a limit on withdrawals to slow a run on savings-and-loans, Maryland officials are seeking a long-range solution to problems facing Old Court Savings & Loan and other privately insured thrifts. An executive order on all the state's privately insured S&Ls allows depositors to withdraw only $1,000 from each account every 30 days. Deposits made after the Tuesday order was issued are exempt.

General Motors, Boeing, Ford, and several defense contractors were expected to have made offers for Hughes Aircraft when bids were privately opened Thursday. Analysts estimated the offers would be in the $4 billion-to-$6.5 billion range. If trustees of the Howard Hughes Medical Institute, which owns Hughes Aircraft, find the bids unacceptable, they may decide to make a public offering of the aerospace company. Sale of Hughes Aircraft would make the medical institute the wealthiest private foundation in the United States.

Two companies that won't be buying Hughes Aircraft: Allied Corporation and the Signal Companies, whose boards of directors unanimously approved a merger Wednesday. The merger was conceived as the companies considered making a joint offer for Hughes. They say they have dropped out of the Hughes bidding.

The Allied-Signal union, if cleared by federal regulators, would make the new company the 16th-largest corporation in the United States. Its specialties would be aerospace, automotive, chemicals, engineering, and construction. Allied would be acquiring Signal for nearly $5 billion in cash, and Allied Signal Corporation would be based at Morris Township, N.J., Allied's present headquarters.

United Press International and the British news service Reuters have met for exploratory talks, and Reuters is believed to have offered to buy UPI. A UPI spokesman said Reuters is one of several companies that have expressed an interest in UPI, which filed April 28 for protection from creditors under federal bankruptcy laws. Reuters reportedly made the offer to UPI creditors Wednesday; UPI refused to confirm this.

A surge in apartment construction offset a slight decline in single-family construction, causing housing starts in April to hit the highest rate in a year. The Commerce Department reported Thursday that housing construction rose 1.6 percent in April to an annual rate of 1.91 million units. While the April increase was below the 14.3 percent rise in March, it still pushed housing activity to its strongest pace since an annual rate of 1.95 million units in April 1984.

Housing construction has benefited from generally stable interest rates since last summer. Since January, interest rates have edged down, and on Wednesday Bankers Trust cut the prime to 10 percent. Other banks were expected to do likewise.

The operating rate at the nation's factories dropped sharply in April, the fourth decline in the last five months, the government reported Thursday. The Federal Reserve Board reported that capacity utilization at United States factories, mines, and utilities declined 0.5 percentage points last month, the steepest drop since a 0.6 percentage point fall last September. This left the total operating rate at 80.6 percent of capacity in April, the lowest level since January 1984.