The ballots have been distributed and voting is already underway. A sizable rally was held by organized labor, in front of San Francisco City Hall this week. The show of strength was a protest against the possible loss of thousands of airline industry jobs at SFO.

United Airlines mechanics are currently members of the Aircraft Mechanics Fraternal Organization, or AMFA. More than 9,000 union members are qualified to vote on a proposal to join the International Brotherhood of Teamsters. "We're a big strong union, AMFA's weak," declared International Brotherhood of Teamsters general president Jim Hoffa. "They've basically given jobs away everywhere they've been."

The stakes are described as high. "There are huge issues for the union members because United continues to go through some ups and downs," explained labor expert Harley Shaiken, director of the Center for Latin American Studies at UC Berkeley. "What happens here will be important in its own right, but could set a precedent for negotiations among similar workers throughout the industry."

12 mechanics at United's maintenance facility at SFO started the campaign to abandon AMFA in favor of the teamsters. Ballots are due by March 31.

KCBS' George Harris reports