A brief warming trend arrived on the picket lines this spring, with workers and management at several major companies suddenly settling contract disputes.
In the past two weeks, 57,000 unionized employees - from tiremakers to airline pilots - have called off threatened or actual strikes against four large US corporations.
The surprise development follows one of the chilliest periods this decade for industrial relations. Labor experts caution, however, that the thaw appears more seasonal than permanent.
The settlements stem in part from the high costs of walkouts. Management worries about dissatisfied customers and eroding profits; workers fear lost income and jobs, labor experts say.
Even Caterpillar and the United Auto Workers (UAW) recently returned to the table after more than a year, hoping to resolve perhaps the bitterest labor dispute of the 1990s.
Elsewhere, some 8,500 striking workers at a General Motors parts plant in Ohio settled with GM last week. Their walkout lasted just 26 hours.
American Airlines pilots on May 5 approved a five-year contract, grounding a strike threat after a brief walkout in February. And striking workers at Chrysler and Goodyear Tire & Rubber recently returned to work.
Yet this budding goodwill hides deep-seated forces likely to provoke more walkouts, say economists and labor experts.
"We're in a testing period for both labor and management," says Thomas Kochan, professor of industrial relations at the Massachusetts Institute of Technology.
A resurgent labor movement is increasingly determined to reverse a 40-year decline.
After steadily backing away from strikes for 15 years, member unions of the AFL-CIO see walkouts as part of an arsenal of tactics. Their aim is to bolster negotiating leverage and their share of the work force.
Unions now represent just 14.5 percent of employees.
Workers themselves express increasing frustration over stagnant wages, say the experts.
For six years, the economy, the stock market, and the salaries of top executives have expanded while wages remain flat.
With unemployment at a 24-year low and job shortages on the rise, workers see an unusual opportunity, say experts.
"People in tight labor markets are bolder about wages than during a recessionary period," says Daniel J.B. Mitchell, a labor economist at the University of California in Los Angeles.
"There has long been a correlation between peaks in the business cycle and strike activity," he says.
Several stubborn long-term trends could also goad workers to the picket lines:
* Competition from low-wage, foreign workers hired by US companies expanding overseas.
* "Outsourcing" production to non-union companies.
*Technology that increasingly replaces human labor.
For now, the will to walkout has diminished since the early 1980s, when employers began hiring replacement workers. The average, annual number of large walkouts is around 35, down from about 300 during the 1970s, according to the US Labor Department.
Risks of walkouts
"Strikes have been a defensive reaction since the early 1980s rather than a tactical advance - they are very, very risky, especially when businesses are so willing to hire replacement workers," says Mr. Kochan.
Replacement workers helped Detroit Newspapers Inc. in February defeat a 19-month strike by 2,500 employees. Reporters and other workers called off the strike and now seek to recover their jobs and back pay through the National Labor Relations Board.
Indeed, most workers cannot expect to triumph by a strike alone. Their arsenal now includes lawsuits, consumer boycotts, shareholder proxies, and other coordinated tactics.
Strikes alone usually bring half a loaf at best. In the recent settlements, many workers grudgingly quit the picket lines.
Two weeks ago, some UAW negotiators walked away from talks with Chrysler rather than endorse the final agreement.
Similarly, American Airlines pilots expressed resentment over a settlement that allowed lower-paid commuter pilots to fly some of their routes, while denying them the right to fly the regional jets.
Targeted strikes at GM
Against GM, the UAW has used "surgical" strikes, staging smaller walkouts that target bottlenecks in the production chain.
Striking workers at two brake plants last year compelled GM to shut down most of its factories in North America. The company lost an estimated $900 million.
Last week, 8,200 workers at a Warren, Ohio, factory that makes wiring and electronic parts won concessions after a one-day strike. Their complaints included job losses to Mexico.
Thousands of other striking GM workers have not prevailed so quickly. Yvonne Smith and 3,500 other GM employees at an Oklahoma City plant struck April 4.
Ms. Smith says GM has cut back on its work force and now requires them to accept excessive overtime, causing an increase in job-related stress and injuries.
"We're getting a good wage, it's just that we want to be able to spend it," says Ms. Smith.
GM says the factory has a strong safety record.