British Airways cabin crew started voting yesterday on whether to take fresh industrial action in their long-running dispute with the airline.
Unite said ballot papers are being sent to more than 10,000 of its members, warning that the bitter row was "deepening".
The dispute was originally over cost-cutting measures, but worsened after BA withdrew travel concessions against cabin crew who went on strike.
Tony Woodley, Unite's joint general secretary, said: "The dispute has been prolonged by vindictive measures directed against cabin crew. In recent months, BA has put nearly 70 loyal workers through hell and sacked 13 of them because they supported their union."
The ballot will close on 21 January.