BA argued to the Electoral Reform Services body, which oversaw the ballot, that Unite was breaching the Trade Union Act Labour Relations (Consolidation) 1992 by launching a ballot whose purpose was "unclear".
A BA spokesman urged the union to return to a peace deal hammered out last year that was rejected by Unite's branches: "There have been enough ballots. It is time for Unite to return to the deal we negotiated, which leaves our existing Heathrow crew the best rewarded in the UK industry, and to put this dispute behind us."