The contrast couldn't be more stark, or more revealing.

Earlier this month, tens of thousands of travelers were stranded at London's Heathrow Airport at the height of the summer season after employees at an airline catering company went on strike over planned layoffs. Hundreds of flights were canceled when British Airways' unionized employees decided to honor the catering employees' picket line.

But here in the United States, Northwest Airlines was able to operate more than 90 percent of its regular flights last week despite a walkout by its 4,400-member mechanics union. Northwest's other unions not only ignored the picket lines, but in some instances pitched in to help 2,000 temporary workers and managers do whatever was necessary to get planes cleaned and repaired and ready to fly. The rival machinists union even took the opportunity to win back from a grateful airline several job classifications that had been "poached" by the more radical mechanics years ago.

And so it goes for the American labor movement. Internal squabbling and declining public support threaten to make this coming Labor Day weekend one of the bleakest for organized labor in a generation. Should Northwest Airlines be able to make good on its threat to replace the striking mechanics, it will be a watershed event in the history of organized labor in the United States -- the first time an airline would have broken a striking union rather than the other way around.

Northwest came into this showdown well prepared. Three months ago, it began training replacement mechanics -- many of whom had been laid off by other airlines -- at a secret facility in Phoenix, while quietly lobbying the Bush administration not to intervene should a strike occur. Once the strike began, replacements were put up in hotels, required to sign confidentiality agreements and bused into airports under tight security.

Both sides see their survival at stake. Northwest, which claims to be losing about $4 million a day, says it will be forced into Chapter 11 bankruptcy protection if it cannot reduce its labor costs by at least $1.1 billion. For the mechanics union, however, its $176 million share would amount to elimination or outsourcing of almost half of its 4,400 jobs.

The lesson will surely not be lost on other unions at economically challenged companies. Last week in Detroit, General Motors, which has lost $2.5 billion in its North American business so far this year, opened talks with the United Auto Workers that could set the template for changes in pay, pensions, health benefits and job security across the entire industry, including key parts suppliers.