"This is the beginning of the recognition that surgery is necessary for the legacy carriers," said Michael E. Levine, a former airline executive who teaches law at Yale University. "And while it's painful, and not all of the surgery will be successful, it's the only way they're going to get healthy."

What ails carriers such as Delta Air Lines Inc. and US Airways Group Inc. more than anything else is the disproportionately high cost of their operations.

This makes it nearly impossible for them to compete with efficient, well-financed and fast-growing carriers such as Southwest Airlines Co. and JetBlue Airways Corp., whose cheap fares have become the standard by which budget-conscious fliers comparison shop. In fact, their larger competitors — whose costs per available seat mile in some cases are more than 30 percent higher than those of Southwest — have slashed ticket prices to unprofitable levels on many routes just to keep their customer bases from shrinking further.

"Pricing power has moved from the airlines to the consumer," said Phil Roberts, managing partner of the transportation consultancy Unisys R2A in Oakland, Calif. "And so what it comes down to, in the end, is the large carriers needing to create a cost base where they can be profitable at these price levels."

With cash reserves shrinking rapidly and earlier efforts to slash expenses proving inadequate, some of the nation's largest airlines are now moving ahead with dramatic transformation plans.

• Delta sketched plans this week to eliminate up to 7,000 jobs, cut employee wages and shed its Dallas hub as part of a $5 billion cost-saving program. The Atlanta-based airline has warned that it could be forced into bankruptcy soon if it cannot stem a recent surge in early retirements among older pilots, who are taking big lump-sum pension payments for fear that their retirement accounts could be wiped out as part of the airline's makeover.

• US Airways made a last-ditch offer to its divided pilots' union yesterday for a new labor contract. It says it needs $800 million in labor concessions to avoid its second Chapter 11 filing in less than two years, and possibly a liquidation. The day of reckoning for the Arlington, Va., carrier could come as early as this weekend. Among other strategic changes, US Airways plans to simplify its fare structure and tweak it's hub-and-spoke route network.

• United parent UAL Corp., which has been operating under Chapter 11 since December 2002, is putting together its third turnaround proposal to a bankruptcy judge. As part of that process, United has threatened to terminate its pension plans to attract additional financing. United CEO Glenn Tilton recently said in a recorded message to employees that the airline could save $625 million a year through new call center, maintenance, airport station and commuter-carrier agreements, though he did not detail how the savings would be achieved.

• Alaska Air Group Inc. on Thursday increased the number of employees it plans to lay off by 750, bringing the total to about 900, as part of a broader plan to save $35 million a year.

Duane Woerth, president of the Air Line Pilots Association, said he is optimistic that the latest moves will be more effective than the post-Sept. 11, 2001, strategy of laying off tens of thousands of workers and getting the remainder to accept lower wages and benefits.

While job and pay cuts remain in the mix this time around, the troubled airlines also appear intent on reshaping their operations from head to toe, he said.

A key factor exacerbating the major carriers' problems in recent months has been the high cost of oil, which makes jet fuel more expensive too. Because fliers are so price sensitive, carriers have been largely unsuccessful at raising fares to pass along the higher fuel costs, magnifying their losses.