The latest twist in the long- running British Airways dispute will be revealed today, when the result of a ballot among thousands of cabin crew over a "final" offer will be announced.
Unite made no recommendation to its members, who have been voting in recent weeks on another attempt to resolve the bitter row, which has led to 22 days of strike action since March, costing the carrier more than £150m.
The cabin crew are not expected to accept BA's offer, raising the prospect of a fresh ballot which could lead to further strikes from September.
The airline will closely study today's result for any evidence of union support draining away, following huge votes in favour of industrial action in previous ballots.
Unite postponed a strike ballot last month after BA tabled a new offer.
However, the union's leadership decided against making any recommendation on whether it should be accepted.
The dispute started last year over BA's plans to cut costs by reducing the number of cabin crew on aircraft.
The row quickly intensified after the airline withdrew travel concessions from staff who went on strike.
Relations worsened after BA took disciplinary action against union members as a result of the dispute, including a number of sackings.
Unite said two of its members were sacked last week, taking the total number of sacked BA crew into double figures.
In a letter to Unite members, joint leaders Tony Woodley and Derek Simpson said: "It is up to you to make up your minds as to whether this offer is acceptable to you as a basis for drawing this prolonged and bitter conflict to a close."