The Boeing Company and Korean Air Lines yesterday announced the biggest airplane order ever placed by a foreign commercial airline-a $1.3 billion contract for up to 18 Boeing 747 jumbo jets.

Korean Air Lines has signed a firm order for 10 of the planes costing a total of $660 million, and an option for eight more planes for $640 million more.

The privately owned Korean carrier, which last week began service from New York to Seoul, will use the planes on that route and on flights from Korea to Los Angeles, Europe, the Middle East and Southeast Asia.

With the Korean sale, Boeing will step up production of 747s to seven planes a month starting in August, said Rusty Roetman, Boeing's director of international sales.

Total Boeing production is expected to reach 28 1/2 planes per month by the end of the year, said William McGinty, a company public relations man. Headquartered in Seattle, Boeing is hiring about 10,000 workers this year, expanding its work force to 91,000 people, McGinty said.

Total employment in the aerospace industry is projected to increase by 100,000 workers this year, the Aerospace Industries Association of America estimated recently.

Based on a survey of manufacturers, the trade association predicted industry employment will exceed 1.1 million workers, the highest since 1969.

The AIA study said the commercial aircraft industry had a backlog of orders totaling $16 billion at the beginning of the year. The strong pace of airplane orders was attributed to improved profits of U.S. airlines as a result of air travel deregulation, increased aircraft utilization because of promotional fares, and the need for newer, quieter planes that use less fuel.

The airplane order signed two weeks ago in Seattle by Korean Air Lines and Boeing is the largest ever by a non-government airline outside the U.S. and the second largest in the industry's history.

The biggest order ever for Boeing-and the business-was a United Airlines contract signed last July for 37 767 and 37 727 planes costing a total of $1.6 billion.

The biggest previous foreign order was a $900 million contract signed last October by Singapore Air Lines for 13 747s and 6 727s costing a total of $900 million.

The Korean order calls for Boeing to build 10 jumbo jets by 1982, with an option for eight more for delivery in 1983 and 1984.

The Koreans are buying four 747F freight planes, three 747-100B high-capacity planes and three 747-200B long-range planes. Two of the freighters and one 747-200B are to be delivered in 1980, one freighter and two of each of the other models in 1981, and another freighter and another high-capacity 747 in 1982.

The 1983-84 option is for two freighters, two long-range planes and two more 747s whose configuration has not been determined.

Both orders include spare parts and the usual training of flight and maintenance crews, Roetman said.

Korean Air Lines will have the high-capacity 747-100B models outfitted with 500 seats and will use them on short-distance flights, from Seoul to Tokyo and Southeast Asia, said C. H. Lee, regional manager for the line.

The planes will be equipped with Pratt & Whitney Aircraft JT9D turbofan engines. The engine order amounts to $110 million on the first 10 planes and another $92 million if the option is exercised, said a representative of the company, which is a subsidiary of United Technologies Corp.

Korean Air Lines already has eight 747s in its 40 aircraft fleet, the second largest in Asia after Japan Air Lines. The Korean's last two 747s were delivered just three weeks ago.

Korean Air Lines is owned by the Hanjin group, a Korean conglomerate with interests in shipping, transportation, insurance, and construction.

For Boeing, the Korean order came as the company faces increasing competition for high-capacity planes from the consortium of European companies which make the Airbus.

Airbus Industrie announced yesterday in Paris that Laker Airways, the cut-rate British airline, has placed an order for 10 Airbuses, each carrying 305 passengers. Value of the contract was not disclosed. CAPTION: Picture, Korean Airlines Eastern Region Vice President M. J. Kim and Boeing Co. International Sales Director Orville Roetman. By Frank Johnston-The Washington Post