NEW YORK — As Delta Air Lines Inc. (DAL) pursues merger talks with Northwest Airlines Corp. (NWA) and UAL Corp.'s (UAUA) United Airlines to form the world's largest passenger carrier, a potential linchpin is thousands of miles away in Paris: Air France-KLM SA (AKH).

The European airline already is an ally of Delta and Northwest in SkyTeam, one of the three major international airline groupings. Air France-KLM also could provide strategic or financial backing in a Delta bid for Northwest, the airline most likely to emerge as Delta's preferred partner, according to people familiar with the negotiations.

Delta's chief executive officer Richard Anderson traveled to Paris after his meeting with Delta directors Friday, when the board authorized him to formally begin merger talks with the No. 5 and No. 2 U.S. airlines by passenger traffic.

Spokeswomen for Delta and Air France-KLM declined to comment on whether Anderson discussed any possible deal scenarios with Air France-KLM while there.

The transactions Delta is considering, according to people familiar with the discussions, would be a stock swap built around current trading prices. While shares of airlines globally have languished because of high fuel prices and broader economic concerns, hearty profits among European carriers now give them more solid financial footing than their U.S. counterparts.

Air France-KLM could provide cash — something U.S. airlines are short on — in return for a sizable stake in the combined carrier. That could sweeten any deal considerably and make it more difficult for a rival suitor to trump any arrangement, these people said.

Federal law prohibits foreign investors from controlling more than 25 percent of the voting equity in any U.S. airline, but taking even a minority stake in a combined major carrier potentially would give Air France-KLM greater access to the United States, according to a person familiar with the airline's thinking.

On the surface, Delta's efforts to pursue consolidation are a straightforward response to the factors that have hurt the U.S. airline industry domestically. Despite record passenger loads in recent months, costly oil and a weakening economy already are raising worries that the domestic industry's resurrection from a five-year depression could be at risk.

But just as significant to building sustainable value among recently sagging airline stocks is international service. During its bankruptcy-court restructuring, Delta, which has a hub in Salt Lake City, cut back many of its problematic domestic routes and placed the aircraft that flew them on more lucrative routes to foreign destinations. International flying has become its most important driver of growth.

At the same time, foreign airlines are emerging as bigger competitive threats. An "open skies" treaty between the United States and Europe is scheduled to take effect in late March, giving carriers such as Air France-KLM, British Airways PLC (BAIRY) and Deutsche Lufthansa AG (DLAKY) greater flexibility to fly to U.S. airports.

And big carriers from Asia and the Middle East are getting a bigger slice of the bustling market for travel between the United States, Europe and fast-growing eastern economies.

Air France-KLM has successfully used its strong hubs to capture a growing share of the busy traffic from second-tier European cities to major international destinations, and it has a stronger cash position than many airlines. As of late September, according to Air France-KLM's midyear financial results, the company had EUR6.2 billion ($9.19 billion) in disposable cash.

The share prices of both companies foundered last year. Before a recent rise because of the consolidation prospects, Delta shares had fallen as much as 45 percent since the airline relisted on the New York Stock Exchange last May. Air France-KLM's American depositary shares on the NYSE in the same period fell by about 40 percent.

Air France-KLM would have strong motivations to help Delta, and has stood firm with its partner before. During Delta's 19-month restructuring, from which it emerged last April, the European carrier offered to assist Delta in unspecified ways, though nothing came of the overture.

Since Air France and Delta joined forces in 1999 and established SkyTeam, they have developed progressively deeper ties. KLM Royal Dutch Airlines of the Netherlands, which Air France acquired in 2004, also has a far-reaching joint venture with Northwest Airlines dating back to 1997. Air France and Delta recently announced they would establish a similar partnership.

Last November, Air France-KLM told investors that by 2010 it hoped to start a "four-way joint venture" among Air France, KLM, Delta and Northwest. The four airlines recently applied for antitrust immunity from U.S. and European Union authorities, which would let them coordinate marketing and pricing in ways normally considered collusive. A ruling in the United States could come by April, according to a Transportation Department spokesman.

Air France's close partnership with Delta also is a strong marketing weapon in its battle against British Airways and Lufthansa. The German airline, in particular, uses its ties within the Star Alliance to build and direct passenger traffic. United — a founder of Star alongside Lufthansa — is the German carrier's heavyweight counterpart in the U.S.

Still, there are obstacles to Air France-KLM playing a major role.

The European carrier is busy trying to acquire a significant stake in struggling Italian carrier Alitalia SpA from the Italian government. Those talks are likely to be difficult. If Air France-KLM gets control of the unprofitable Italian carrier, turning it around will require significant financial resources and management time.

If Delta were to strike a deal with United and defect from SkyTeam, the move would be a double blow to Air France-KLM. It would rob Air France of its main partner in the United States, boost Lufthansa's U.S. partner and help the German carrier.