BA cabin crews vote to strike

Job action to begin "after Dec. 21."
Evidently, more than 1 union represents BA flight attendants. Article says "over 2500" cabin crew voted to strike. BA is a huge airline. AA has twice that many flight attendants just based at DFW. Explanation anyone?

I think the 2500 FA mentioned in the article are those that work BAs short haul flights ("Mixed Fleet").

Unite is the trade union that represents BA cabin crew (FAs) as well as FAs at a couple other airlines. I'm guessing that the British Airlines Stewards and Stewardesses Association (BASSA) branch of Unite (which I believe also includes the Mixed Fleet) is the largest.