The Association of Flight Attendants-CWA (AFA), which represents 28,000 flight attendants at the Chicago-based carrier, said the vote will open on Aug. 1 and close on Aug. 28.
The last contract became eligible for an amendment in August 2021.
"United flight attendants can't afford to wait for improvements," said Ken Diaz, president of AFA's United chapter.
"We deserve an industry-leading contract, and we are ready to show United management that we will do whatever it takes."
United did not immediately respond to a request for comments.
The union said strike authorization votes have helped expedite contract negotiations at rivals Alaska (ALK.N), Southwest (LUV.N), and American Airlines (AAL.O).
United's flight attendants, who filed for federal mediation last year, are demanding double-digit base pay increase, higher pay for time at work including on the ground, retroactive pay, schedule flexibility and work rule improvements.
Even if the flight attendants authorize a strike, they cannot walk off the job until the National Mediation Board (NMB) grants them permission.
The board will first have to determine that both the parties are at an impasse and further bargaining would not be productive. This lengthy and complex process makes it rather difficult for airline workers to strike.
Last year, the NMB denied a request from the flights attendants of American Airlines to be released from federal mediation.
