Some 1,700 workers at helicopter firm Agusta Westland took part in a 24-hour strike on Friday of last week.
The workers, members of the new Unite union, are protesting at plans to change the way pensionable salary is calculated, and company attempts to close the final salary scheme to new entrants.
The firm, which is the biggest employer in Yeovil, Somerset, currently claims a £94 million shortfall in its final salary scheme.
It has offered to put £30 million into the scheme but wants workers to make up the rest.
There were some 100 people on a lively and determined picket line.
It is the first in a series of four one-day strikes planned by unions, which will also see workers working to rule.
The company introduced changes to the scheme in May this year.
The previous scheme was based on employees’ final salary.
But this has been replaced with a direct contributions scheme, which depends on how much money staff have paid into their pension.
Pensions are now based on an average wage over a set number of years rather than an employee’s final salary, leading to a reduction in some cases.
The workers are worried that the plans, which will alter how their pensions are decided, will reduce the value of their pensions and will exclude new members of staff from the current scheme.
Unite representative Colin Rose said feeling was high and staff had voted overwhelmingly in favour of industrial action.
The union has been in talks with the company on the pension situation since 2006, but has said Westland had proved unmoveable on the two fundamental issues for members.
Colin Rose, said, “Our members are happy to make greater contributions to the scheme, but we cannot accept a proposal to backdate the pensionable pay arrangements or to prevent new members from joining the scheme.
“If implemented these changes would have the combined effect of reducing the value of contributions already made, and of creating a two-tier workforce at Agusta Westland.
“We need to make clear to the company that our members are determined to protect these two fundamental principles.
“The mood is determined but we do want to find a result.”
The Finmeccanica Group, the owners of Westland, made a profit of £690 million in 2006.
There are further strikes planned for Wednesday 29 August, Tuesday 11 September and Monday 27 September.