Aluminum Co. of America, the nation's No. 1 aluminum manufacturer, yesterday reported a first-quarter loss of $14.3 million, but the company expects business to improve later this year because of increased housing starts and auto production.

Among other reports:

* Apple Computer Inc. said its fiscal second-quarter profits soared 73 percent from a year earlier, while sales climbed 74 percent. Net income rose to $23.9 million (40 cents a share) from $13.8 million (24 cents) a year ago. Sales increased to $228 million from $131 million.

* American Airlines reported a loss of $28.1 million for the first quarter of 1983, compared with a loss of $41.6 million in the first quarter of 1982. Total revenues for the 1983 quarter rose 8.5 percent to $1.04 billion, from $956.9 million in the first quarter of 1982. Total expenses for the 1983 quarter rose 5.9 percent to $1.07 billion from $1 billion in the first quarter of 1982.

* Dow Chemical Co. reported lower first-quarter earnings of $69 million (36 cents) on sales of $2.54 billion. In the year-earlier period, the company earned $154 million (80 cents) on sales of $2.78 billion.

* R.J. Reynolds Industries Inc. reported a 14 percent drop in earnings despite a 19 percent gain in 1983 first-quarter sales.

* Textron Inc.'s first quarter earnings were up slightly as a result of cost-cutting, increased productivity and lower interest costs, the conglomerate said. The company reported earnings of 60 cents a share for the first quarter of 1983, up 3 cents from the first quarter of 1982. Net income increased 7 percent, to $22.3 million. Textron sales for the first three months of this year were down 7 percent, to $717 million.

Alcoa's loss compares with red ink of $33.7 million in the fourth quarter of 1982. The company earned $43.8 million (57 cents) in the first quarter of 1982, but those results reflected a one-time gain from the exchange of stock for sinking fund debentures.

For all of 1982, Alcoa had an operating loss of $60.8 million on sales of $4.6 billion. Net income was $10.8 million. Sales in the first three months of this year totaled $1.1 billion, compared with $1.2 billion in the year-ago period.

Chairman Charles Parry said the first-quarter improvement reflected a jump in orders as aluminum customers replenished depleted inventories.

Apple earnings for the first half of its fiscal year rose to $47.4 million (80 cents) from $27.4 million (48 cents) in the comparable year-earlier period. Six-month sales rose 67 percent to $442.3 million from $264.6 million.

Apple president and chief executive A.C. Markkula Jr., who is being replaced in those posts by former Pepsi-Cola Co. president and chief executive John Sculley, attributed the improved results in part to the recently introduced Apple IIe personal computer.

"Demand for the Apple IIe exceeded our expectations, causing temporary shortages at the retail level," he said in a statement. "We have accelerated production of this system at both our domestic and European plants to meet growing market requirements."

Markkula said introduction of the company's Lisa system, an advanced personal computer aimed mainly at business, also is expected to enhance profit this year.

Dow President and Chief Executive Officer Paul F. Oreffice said that despite the decline the company realized substantial improvement from the 1982 fourth quarter.

"We are on the trail of economic recovery, but it's important to note that business in the chemical industry traditionally lags a general economic turnaround by a few months," Oreffice said. "However, we are encouraged by the steadily increasing daily sales rate of our principal products each month."

Oreffice said Dow's European business experienced a healthy first-quarter gain and "sets the recovery pace" for the United States.

Reynolds' first-quarter net earnings of $159 million were $26 million behind last year's $185 million. While the common-share price dipped to $1.27 from $1.69, net sales and revenue for the three months ended March 31 totaled $3.43 billion, compared to $2.87 billion the previous year.

Chairman and chief executive officer J. Paul Sticht said there were several reasons for the decline.

"We indicated previously that a combination of factors including the doubling of the federal excise tax on cigarettes, softening energy prices, a substantial change for a voluntary separation program and dilution attributable to the Heublein acquisition would result in a difficult comparison," Sticht said.