Amicus members at the Rolls Royce plant at Filton, in Bristol, are to vote on industrial action in a dispute about the sacking of an union convenor.
Following an unsuccessful internal appeal hearing for Jerry Hicks ealier this week, 95 Amicus test engineers working on the site will be balloted from 3 August.
If they vote in favour, action at the site could start as early as 17 August.
Amicus said it cannot rule out the possibility that the dispute could spread after its senior convenors in aerospace and shipbuilding, representing more than 70,000 union members, met yesterday to offer their support.
Rolls Royce took the decision to sack Hicks after a disciplinary hearing which concluded last week. The union claims he was targeted because of his work as a trade union official.
Ian Waddell, Amicus national officer for aerospace, said: “We regard this decision as blatant and unacceptable victimisation of a trade union activist.
“We are balloting for strike action at the test area in Filton, and we will keep our options open to extend the action to other sites.”