Unite has targeted emergency talks with BAE Systems after media reports the defence manufacturer could cut 3,000 jobs in the UK.
Ian Waddell, Unite's national officer for aerospace, said:
"These job losses would be a hammer blow to the UK defence industry, which is already reeling with the consequences of the government's "buy off the shelf" policy."
He added: "We will be seeking urgent talks with BAE Systems to try and clarify where these jobs are under threat, and to work with them to avoid compulsory redundancies wherever possible."
The comments follow reports of BAE job cuts at www.guradian.co.uk. BAE's military aircraft division in Warton, Lancashire which produces the Typhoon fighter jet would be worst hit according to The Guardian.
BAE was unavailable for comment.