Northwest-KLM Joint Operation Cleared by U.S. : Airlines: The two will be allowed to function in most ways as a single airline.

The Department of Transportation Monday gave tentative antitrust clearance that would let KLM Royal Dutch Airlines and financially troubled Northwest Airlines Inc. operate as if they were a single airline.

The DOT issued a show-cause order asking for comment on both sides of the issue but said that the proposed agreement between the two airlines appeared to benefit the public. If it approves the agreement, the agency said, it would review it in five years to determine its impact on competition in the airline industry.

The proposal to integrate the operations of the Netherlands-based KLM Royal Dutch and Northwest, the fourth-largest U.S. carrier, comes at a time of airline industry financial hardship that Northwest has felt acutely. The DOT’s announcement came on the same day Northwest said it will cut an additional 565 people from its work force, bringing total layoffs to more than 1,800. However, the airline also has hired 900 flight attendants. Monday’s cutbacks include about 350 management jobs and 215 union-represented positions.

Airlines around the world are building alliances for what appears to be the coming global consolidation of the industry into a few strong worldwide carriers. DOT still has before it the question of whether to allow British Airways to make a $750-million investment in USAir Group Inc. that would give it 44% ownership and 21% of the voting rights in the Arlington-based carrier.

KLM bought an interest in Northwest shortly after Northwest’s current owners bought it in a deal that increased the airline’s debt. KLM owns 20% of the common stock in NWA Inc., Northwest’s parent company, and 10% of its voting shares. At the time the transaction was approved, DOT sought to limit KLM’s control of Northwest.

Now the airlines are proposing to schedule their flights together, to consult and cooperate on pricing, to advertise and market together and otherwise make their operations indistinguishable to the competition.

Winning the Transportation Department’s tentative approval for the deal was made easier by the fact that the United States and the Netherlands have agreed to give unlimited access to each other’s airlines markets.

Glen Engel, an airline industry analyst with Goldman Sachs & Co., said the relationship would be a plus for Northwest.