Right to vote
A. Lurker,
According to the DirectGov website section on industrial action,
"The right to vote is given to all members the trade union intends to ask to take part in the industrial action"
This does not include those members who will be leaving the airline prior to industrial action by, for example, VR.
As mentioned above, it's only really a problem if the numbers involved are enough to affect the outcome of the vote.