Air New Zealand is threatening to ditch IT provider IBM after a massive systems failure disrupted the airline's entire operations on Sunday.
The IT failure occurred about 9.30am on Sunday, knocking out the airline's computers for five hours and affecting its call centre, website and check-in kiosks.
Air New Zealand staff were forced to resort to manual ticketing and processing after a back-up generator at IBM's Newton plant in Auckland failed.
About 10,000 customers faced long delays on the last day of the school holidays and the passenger backlog was not cleared until 4pm.
In an internal email to staff, airline chief executive Rob Fyfe has revealed his fury over the outage and IBM's apparent unwillingness to take responsibility.
Mr Fyfe says in his 30-year working career he cannot recall a time when a supplier has been so slow to react to a catastrophic systems failure which left Air New Zealand high and dry.
Mr Fyfe says he expected more of IBM and the airline is now reviewing its options for an IT supplier the company can have confidence in.
IBM says the outage only lasted a couple of minutes and believes a failed oil pressure sensor on the back-up generator may be to blame.
In a statement on Monday, IBM says it has not yet established exactly what went wrong and has hired an independent expert to investigate fully the cause of the outage.
The statement also includes an apology to IBM's clients and customers.