Union negotiators have left town, leaving a federal judge as Northwest Airlines Corp.'s last hope to block a flight attendant strike that could begin as early as Friday night.

Flight attendants are angry that Northwest imposed pay cuts and work rules that the rank-and-file had rejected, and they say they'll begin sporadic, unannounced strikes anytime after 9:01 p.m. CDT Friday. Northwest, already operating under bankruptcy protection, has said a strike like that could kill it.

Just nine hours before the strike deadline, U.S. District Judge Victor Marrero will have to make a snap decision on whether to intervene. Marrero will grapple with obscure provisions of labor law, but the core question is: Can airline employees walk off the job after their bosses unilaterally cut their pay and change their work rules?

Marrero's job will be complicated by the Norris-LaGuardia Act, which generally bars judges from blocking strikes. Bankruptcy Judge Allan L. Gropper, who has spent much of the past year overseeing Northwest's reorganization, agreed that a strike could kill the airline, and that both sides would benefit from more time to cool off. But he found that the Norris-LaGuardia Act bars him from stepping in.

The Association of Flight Attendants said its strike preparations were gaining momentum, and it has been holding classes all week in cities where Northwest flies to train flight attendants on its "CHAOS" strike strategy, for "create havoc around our system."

More than 300 flight attendants showed up for a single class in Detroit, and union officials said hundreds of flight attendants have attended the classes in Minneapolis. Northwest has some 7,300 active flight attendants.

The union has said firing any who strike would be illegal. Northwest spokesman Kurt Ebenhoch wouldn't comment on that.