Qantas staff are threatening to disrupt the Australian airline's flight schedule during the Christmas period over its plans to establish air crew operations in London.
The Flight Attendants Association of Australia (FAAA) has warned it will strike over the holidays unless Qantas promises to limit the number of airline crew based in London.
The union's fears about job security were further fanned by Qantas's admission last week that it has been secretly training a force of 350 strike-breakers on short-term contracts to counter such industrial action.
Qantas's managing director, Geoff Dixon, told the airline's annual meeting last Thursday that the London crew base would create savings of at least A$18m (£7.3m) a year through lower costs and greater productivity.
Telling shareholders that "no crew jobs are at risk as a result of this decision", Mr Dixon dismissed the union's job-security concerns. "Even after the establishment of the new London cabin crew, over 90 per cent of Qantas's jobs will remain in Australia," he said.
The FAAA's divisional secretary, Michael Mijatov, said he was concerned that as many as 1,000 crew positions would be relocated to London.
"We hope they see sense but if they are not going to give us adequate guarantees, then we will take action," Mr Mijatov said.
Qantas has a 370-staff limit on overseas crew until the union's enterprise bargaining agreement runs out on 17 December.
Qantas announced in June that it would set up a London base with about 400 airline attendants from June next year.
However, leaked internal documents reportedly showed back in May that Qantas had well-advanced plans to relocate one-quarter of its international crew, roughly 1,000 attendants, offshore.
Another union, the Australian Services Union, has also threatened industrial action over the airline's decision to raise the cap for non-executive directors' pay by 66 per cent to A$2.5m.Reuse content