The first Saab-Fairchild 340 turboprop airliner rolled off the assembly line yesterday in Linko ping, Sweden, the product of an unusual joint venture between American and Swedish aircraft companies.

The 34-passenger twin-engine plane, unveiled yesterday by Sweden's King Carl XVI Gustaf, is being produced on a 50-50 basis by Fairchild Industries of Germantown, Md., and Saab-Scania.

In a recent interview, A.J. Spuria, senior vice president of Fairchild's commercial aviation group, explained that Fairchild and its subsidiaries build the wings and tail and supply the interiors and seats, and Saab-Scania builds the fuselage and is responsible for the plane's final assembly at its new Linko ping plant.

The two companies also have split the aircraft's marketing, with Fairchild taking North America and its Swedish counterpart taking the rest of the world, Spuria said.

Designed for the burgeoning regional airlines, the aircraft has already chalked up more than 100 orders; when 200 are sold, the joint venture breaks even, Spuria said. Officials of the joint operation think potential sales could run to 650 aircraft through 1992. The profits are to be shared equally by the partners.

The plane that rolled out yesterday carried the colors of the venture's first two customers--Air Midwest, a commuter carrier based in Wichita, Kan., and Crossair, a Swedish carrier whose order launched production of the 340. The first plane is scheduled for its maiden flight in early 1983, with deliveries to Crossair to start in early 1984.

The plane is to be flight tested for certification simultaneously by regulatory authorities in Europe and the United States.

Like other new planes coming on line, the pressurized 340, powered by two General Electric Co. engines, uses the latest technology to economize on fuel and lower operating costs. The 340 incorporates an advanced wing design, modern lightweight composite materials and a digital avionics system similar to those being used in the newest Boeing Co. aircraft.

The plane is also being made available by Saab-Fairchild as a business aircraft with versions seating between 14 and 24.

Saab-Scania is the producer of the Viggen, a military aircraft ordered by the Swedish Air Force.

In another development, Fairchild announced it has filed a "shelf" registration statement with the Securities and Exchange Commission covering $100 million of debt securities. Fairchild said it may offer the securities periodically, depending on market conditions, at prices and terms to be set at the time of sale.