NEW YORK, DEC. 23 -- Pan Am Corp., seduced and then abandoned by a succession of suitors this year, faces an uncertain future following the collapse of the latest takeover proposal from Braniff Inc.

The beleaguered airline company could try to turn itself around or it could look wistfully for yet another potential rescuer, observers said today, noting that much will depend on the strategy of the company's unions and the direction of its leadership.

Pan Am, saddled with debt of about $950 million and continued losses, bears little resemblance to the powerful global airline empire started in the 1920s and run for many years by the legendary aviator Juan Trippe.

Pan American World Airways -- the company's main airline subsidiary, which operates mostly between the United States and foreign cities -- suffers from a lack of domestic routes, which are more lucrative. Pan Am's few financial bright spots include its Northeast shuttle service, which operates among New York, Boston and Washington in competition with Eastern Airlines, and its Pan Am Express commuter airline.

Pan Am agreed with Dallas-based Braniff late Tuesday to terminate a letter of intent for a merger that the two companies signed Dec. 7. Pan Am's board met for 2 1/2 hours today, but the company did not issue a statement on what was discussed.

Braniff's takeover proposal had the support of Pan Am's board. But the Pan Am pilots union rejected it, sources said, chiefly because of objections to Braniff's plan for obtaining $800 million in wage concessions from Pan Am unions over four years.

Braniff's withdrawal was the latest chapter in a saga of proposed and potential Pan Am takeovers, including overtures in recent months from Anglo-French financier Sir James Goldsmith, West Coast investor Kirk Kerkorian and New York real estate developer Donald Trump.

And early this year, Pan Am officials discussed with American Airlines and other carriers a possible sale of all or part of the company.

Pan Am now is left with only a possible hostile takeover bid from Towers Financial Corp., a New York debt-collection and insurance holding company.

Despite Towers' repeated announcements regarding a possible bid, it is regarded by Wall Street as a questionable suitor with uncertain ability to muster the capital to acquire Pan Am.

"They have to really show that they have the financial wherewithal to carry this kind of project out," said Andrew Kim, an airline analyst for Eberstadt Fleming.

Towers has not launched a formal offer for Pan Am and has not fully identified the source of its proposed financing for such a bid. Pan Am, in turn, has not publicly acknowledged Towers' interest.

Towers announced Tuesday that it had enlisted the support of the pilots union and the Teamsters, two of the five labor unions at Pan Am. Towers also said it had lined up $350 million in financial backing in addition to the $50 million it announced several weeks ago. It declined to identify its backers.

The Pan Am unions -- especially the pilots -- will play a critical role in the company's survival. The pilots seem to have been instrumental in defeating the Braniff proposal, overriding the Pan Am board's approval of it because they objected to Braniff's wage concession plan.

"You have to get the unions' approval," said Anthony Hatch, an analyst for Argus Research Corp. "The key to all this has been concessions."

Pan Am needs substantial union-approved wage cuts to pull itself out of the financial quicksand, observers say.

Also key to Pan Am's future is the shape of its leadership. Sources say that C. Edward Acker, the company's chairman, has incurred the wrath of both the unions and elements of management -- creating an embarrassing rift between Acker and vice chairman Martin Shugrue.

That has fueled speculation that the board could oust Acker as part of a strategy to turn Pan Am around.