But this vote doesn't mean they will go on strike.
"It would be at minimum a 30-day period before we would be permitted to strike," said Kristie Rivera, President of the Association of Flight Attendants-CWA or AFA Council 11-San Francisco. The Association of Flight Attendants-CWA voted to authorize a strike.
"United obviously doesn't want that. Flight attendants don't want to have to go on strike, but we will use whatever means are necessary up to and including a strike so that we can propel our negotiations forward."
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United flight attendants are demanding better pay, pay for all the time they're at work, schedule flexibility and more.
SFO is one of 20 airports across the country where flight attendants set up informational picket lines Wednesday.
Liam Horgan demonstrated at SFO. Horgan has been a flight attendant for United for just over a year.
"Making the amount that we do and working the amount of hours that we have away from home and still being unable to make ends meet is entirely upsetting to me and to a lot of flight attendants," Horgan said.
"There is billions of dollars in revenue and profit at this airline," Rivera said. "Flight attendants are only asking for their fair share."
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United Airlines sent this statement:
"We continue to work toward an industry-leading agreement for our flight attendants, including negotiations this week and every month through November. Both sides have been actively engaged in these negotiations facilitated by the federal mediator requested by the union. We remain eager to reach an agreement.
To be clear, there is no work stoppage or labor disruption. Instead, off-duty flight attendants are exercising their right to conduct an informational picket. Federal law bars a strike until after a lengthy process that includes a release from mediation, which can only be granted by the National Mediation Board."
This all happening as the Labor Day travel kicks off Thursday through Tuesday. SFO is expecting an almost 9% increase in travelers over last year for the holiday weekend.