Dan A. Colussy, former president of Pan American World Airways, will take over the helm at Western Airlines if it is acquired by UNC Resources Inc., the Falls Church company said yesterday.

UNC said Colussy, whose resignation at Pan Am was effective Dec. 1, has been working jointly with Keith A. Cunningham, UNC's president and chief executive officer, in pursuing the proposed merger with Western and would assume "active management of Western" if a combination occurs.

The unexpected UNC bid was made public by Western on Dec. 24. Colussy's involvement was not disclosed before because of an agreement with Pan Am that barred him from employment in the airline business until Jan. 1. p

When he left Pan Am, Colussy began to look at opportunities in the airline industry with a view to "running my own company," he said in an interview yesterday. Colussy and Cunningham were brought together by an investment banker who knew of Cunningham's desire to see UNC diversify.

UNC Resources is a holding company for United Nuclear Corp., a diversified energy company whose activities include uranium mining and milling, nuclear manufacturing, providing products and services to the commercial nuclear power industry, and oil and gas exploration and development.

If UNC is successful in its bid for Western, it will be the first time a non-airline industry since deregulation. UNC said a combination with Western would offer the shareholders of both companies a diversity of opportunities that would be mutually advantageous.

"For Western, the result would be a company with a substantially greater asset base, not entirely tied to the airline industry. For UNC, the result would be more diversified company, better able to take advantage of an upturn in the national economy, the time when airline earnings are traditionally at their strongest," a company statement said.

UNC said yesterday it has not received a respone to its proposal from Western but hopes for one soon. A Western spokesman said the matter still is being considered. The next regularly scheduled meeting is Jan. 26.

Western seemed to Colussy to be the right airline for this move. "In my opinion, Western is one of the better-situated airlines to move ahead in a deregulated environment," he said. Its fleet of airplanes is among the best in the industry because they are relatively new, he said, and its route system is concentrated in a part of the country that is expected to continue strong growth.

Colussy doesn't think Western's merger agreement with Continental Airlines, now pending before the Civil Aeronautics Board, is a major barrier. Although Western has a "perfectly legitimate merger agreement with Continental," it has not secured shareholders' approval for it, Colussy pointed out.

He said UNC's offer will be of "sufficient interest" that the board of directors will find it in the best interests of the shareholders to present the UNC offer to them -- alongside the Continental offer, should the CAB and the president approve the proposed Western-Continental combination. (The CAB turned down a previously proposed Western-Continental combination in July 1979. A merger between an airline and a non-airline concern doesn't need CAB approval.)

Colussy and UNC declined to elaborate on their offer to Western. Officials of the Los Angeles-based airline said earlier that UNC offered to provide Western shareholders with a combination of cash and UNC securities that would yield them about a 50 percent premium above the last several months' average market price of the Western stock. Western's common stock has ranged between $6 and $11.63 during the last year and closed Mondat at $8.63 in New York Stock Exchange composite trading.

Colussy said UNC has acquired 4.9 percent of the stock of Western, just below the 5 percent reporting threshold requirement of the Securities and Exchange Commission.