The shakeout in the global airline industry has moved forward like a slow-motion train wreck since Sept. 11, 2001, but last week the pace quickened considerably.

On Sunday, US Airways filed for bankruptcy protection for the second time, with its emergence from Chapter 11 anything but certain. The next day, the airline warned a bankruptcy court it may freeze or terminate two pension plans covering 25,000 workers and former employees.

Fresh from its promise to cut 7,000 jobs, slash wages and dump its Dallas hub, Delta Air Lines received a positive sign Tuesday when its pilots union agreed to find a deal to stem the exodus of senior pilots threatening to push that carrier into bankruptcy.

But on Wednesday, the airline confessed that its auditors had questioned its ability to "continue as an ongoing concern," following losses of more than $5.6 billion since 2001. Weighing Delta's cost-cutting promises against auditor concerns, Standard & Poor's and Fitch Ratings lowered the credit rating of the nation's third-largest carrier.

On Thursday, UAL chief executive Glenn Tilton flew to Brussels to deliver the grim news that United Airlines would have to cut expenses by $655 million, a figure considerably higher than earlier cost-cutting targets. Tilton suggested the United States must follow Europe's lead and allow its enfeebled air carriers to begin merging.

Then, as United's chief financial officer, Jake Brace, emerged from a court hearing Friday, he delivered another blow: The nation's second-largest carrier would actually need to save $500 million above that $655 million to stay alive. About 6,000 jobs may be on the line, as well as the company's pension plan.

Across the pond, the news wasn't much better. Italy's Alitalia announced labor agreements Thursday to shed 2,500 jobs, cut wages and extend pilots' flying hours. British Airways canceled almost 1,000 flights from Heathrow Airport over the next three months, after cost-cutting efforts slashed so many jobs that the airline found itself short-staffed.

It is now inconceivable that the airline industry of the near future will look anything like it did just four years ago. But just what the industry of tomorrow will look like is anything but clear: a herd of low-cost carriers leaving travelers to hopscotch across the globe? One or two higher-cost airlines surviving the shake-up?

At least consumers are getting the best of both worlds -- big carriers with long flights competing on price with the smaller upstarts that threaten their existence. But that's for now.