After record earnings in 1978, Pan American World Airways looks at 1979 with "guarded optimism," Chairman William T. Seawell told shareholders at the annual meeting here today.

"We expect a good year in 1979 - barring a serious recession - but perhaps not so good a year as 1978," he said.

The airline's record showing last year - net income of $119 million - was related to its ability to hold on to its share of the market in spite of increased competition, to reasonable control of costs and to impact of a lengthy Northwest Airlines' strike, he said.

But this year, Pan Am expects a reduced rate of traffic growth, escalating fuel prices and other cost pressures, increased competition or even more routes, and a substantial loss of business that they had expected to generate by their services to Iran, now reduced from 14 flights a week to five, Seawell said.

He reiterated Pan Am's position that a merger with National Airlines would produce an entity better able to compete against foreign airlines which are gaining increased access to U. S. markets under the Carter administration's pro-competition policy.

"We are the only major international airline in the world without a strong domestic or regional system to feed its intercontinental flights," Seawell complained. Although he conceded Pan Am could probably get authority to build to domestic system, he repeated his contention that it wasn't feasible to start from scratch. "We need a functioning system and we need it now," he said. CAPTION: Illustration, The Market In Brief, May 8, The Washington Post