Ford Motor Co. lost $355.4 million in the first quarter, an improvement for the nation's second-largest automaker over the $439.5 million loss in the same period a year ago.

The last time Ford had a quarterly profit was in the second quarter of 1981, when it earned $60 million. That profit was Ford's first since the third quarter of 1979.

Ford's total sales declined 4.3 percent for the latest quarter to $8.92 billion from $9.32 billion.

Among other major companies reporting first-quarter earnings yesterday were Eastman Kodak Co., Pan American World Airways, National Steel Corp., and PepsiCo Inc.

Ford's loss was due to the depressed U.S. economy and an 18 percent decline in industrywide car sales despite extensive rebate and buyer incentive programs, Ford Chairman Philip Caldwell and President Donald E. Petersen said in a joint statement.

Ford, which analysts had predicted would lose up to $400 million in the first quarter, was the third major U.S. automaker to announce first-quarter results.

General Motors Corp. announced a profit of $128.3 million, down 33 percent from a year ago, while American Motors Corp. said it lost $51 million compared with $52.7 million in the 1981 quarter.

In the United States, Ford lost $506 million in the first quarter, up from $395 million in the 1981 period, but the company's $52 million loss in Canada was down from $61 million in the year-ago period. Outside North America, the automaker earned $203 million, up substantially from a profit of $17 million in the same quarter last year.

The improvement overseas was due to "lower operating costs and higher unit volume arising from increased dealer stocks in Europe and higher car shares in most major markets throughout the world," Caldwell and Petersen said.

Eastman Kodak Co. earnings in the first quarter were down 27 percent from a year ago, the company said yesterday, and it blamed the slide on the worldwide recession and the strength of the dollar.

Kodak said net income fell to $181.3 million ($1.12 a share) from $249.1 million ($1.54) in the comparable period of 1981. Sales fell 3 percent to $2.25 billion from $2.31 billion.

The company said its photographic division had sales of $1.78 billion, down 4 percent from a year earlier. Shipments were flat in the United States but declined "significantly" in Europe, Kodak said.

The chemicals division posted a 1 percent increase in sales to $531.2 million, but volume of shipments was down.

Pan American World Airways yesterday announced a loss of $127.3 million in the first quarter compared with a loss of $114.5 million a year ago, when earnings of International Hotels Corp., since sold, reduced the loss from $121.6 million.

Revenues fell 2.4 percent from a year ago to $853.8 million. Operating expenses declined 0.9 percent to $953.9 million.

Airline revenue was down 3.6 percent, and airline operating costs fell 1.8 percent.

Chairman C. Edward Acker said the results reflect a 2.7 percent decline in scheduled passenger traffic and a $2.3 million loss on foreign currency translations. He said lower passenger traffic yields because of competitive fare-cutting were a big factor in the losses.

National Steel Corp. lost $40.2 million for the first quarter, as it shipped the smallest amount of steel in two decades.

National, the nation's fourth-ranked steel producer, earned $15.7 million (83 cents a share) in the first quarter of 1981.

Revenue declined 22 percent to $831 million from $1.1 billion for the same period a year ago.

National blamed the recession and imported steel for reducing demand and dropping prices to abnormally low levels.

Although it didn't break down the earnings, National said its aluminum and financial services businesses were profitable in the first quarter, but its steel group had a substantial loss.

National said its steel plants operated slightly above 50 percent capacity as steel shipments declined 28 percent to 1.3 million tons from 1.9 million tons a year ago.

PepsiCo Inc., a leader in the soft-drink industry, said yesterday that its profits rose 6 percent in its first quarter on a 14 percent increase in sales.

PepsiCo said that profits for the 12 weeks ended March 20 were $60.1 million (65 cents a share) compared with $52.8 million (58 cents) in the year-ago quarter. Sales increased to $1.56 billion from $1.47 billion.