Planes could be grounded and banking systems disabled after negotiations failed between IBM and staff in its Baulkham Hills “Flightdeck” facility.

Qantas, Cathay Pacific, Air New Zealand and Westpac, along with government agencies Medicare and Customs, are some of the businesses that face critical IT and infrastructure outages if strikes planed for Thursday go ahead.

Workers are represented by the Australian Services Union (ASU) which has pressured IBM for employee collective agreements which include equitable pay rises, redundancy packages, penalty rates and leave entitlements.

ASU branch secretary Sally McManus said IBM has flatly refused to accept the collective agreements since negotiations began in May this year.

“They point blank refused to meet with us in May, and they refused in a meeting in May to enshrine anything in a collective agreement or agree to any pay increases,” McManus said.

“IBM told us today that they won't negotiate or meet with us if we plan to strike, but there's no point of meeting if they won't move on anything.

“IBM wants everything in policy so they can change things in a whim; redundancy pay is now under review with no discussions with staff. Some staff haven't had a pay rise in six years.”

McManus said IBM is putting the reputation of its customers at risk because they will be unable to process online transactions, including money transfers and bookings.

At the Baulkham Hills facility — known as “Flightdeck” because the rows of computers resemble an aircraft flight deck — workers maintain critical applications and continually fix errors to maintain smooth service operations for some of IBM’s biggest customers. This is a key bargaining chip for the ASU, according to McManus.

“Airport customers will face flight delays, billions of dollars may not be processed for Westpac, and Customs won't be able to keep track of security checks, all because IBM refuses to talk to its employees,” she said in a statement.

“Every one of the IBM customers has collective agreements so I would imagine they will be pretty annoyed that their business is at risk because IBM refuses to work with us.”

The strike was agreed upon last Friday after the results of a two-week long secret ballet drew 87 percent support for indefinite strikes. The action will begin with rolling four-hour work stoppages and will be escalated if IBM “doesn't budge”.

IBM raised objections with the Australian Industrial Relations Commission in July that the ASU should not be allowed to represent Flightdeck workers.

IBM spokesman Caspian Smith said in a written statement that it will maintain service level agreements with customers.

"We are engaged in ongoing discussions with employees at the site in question to address any issues directly, and we will continue to maintain service levels to our clients," he said.