Air New Zealand had planned to close its London base in October but now it will close on Friday.

Air New Zealand will close its London cabin crew base of 130 flight attendants on March 20, seven months earlier than planned, due to the impact of coronavirus is having on global travel.

Air New Zealand had planned to close the base when it withdrew from the daily Los Angeles-London route in October 2020.

Its London-based cabin crew will now operate a final service on the route on March 20 before a New Zealand-based crew takes over to operate the remaining leg of the flight (Los Angeles-New Zealand) on March 21. The LA route will then be suspended until June 30.

An Air New Zealand spokesman said the staff would no longer be employed by the airline as of March 31.

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Air New Zealand is also suspending its Buenos Aires route with immediate effect, following increased government restrictions for travel into Argentina.

NZ31 (Buenos Aires-Auckland) departing Ministro Pistarini Airport at 11.45pm on March 18 local time will be the airline's final service until June 30.

Air New Zealand shares were placed in a trading halt on Monday to allow time for the airline to assess the impact of the New Zealand Government's new travel restrictions designed to stop the spread of Covid-19.

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On Wednesday the trading halt was extended until either an announcement was made by the company or market open at 10am on Friday.

On Monday at 1am the Government introduced restrictions requiring everyone arriving in New Zealand to self isolate for 14 days.

Air New Zealand responded by announcing plans to reduce its long-haul capacity by 85 per cent and its trans-Tasman capacity by 80 per cent from March 30 until June 30. Its domestic capacity will be reduced by around 30 per cent in April and May.

With the airline bleeding cash and Air New Zealand chief executive Greg Foran warning that up to 3750 jobs could be lost, a bailout package from the Government is expected to be announced any moment.

Air New Zealand chief pilot David Morgan said the suspension of Buenos Aires had been brought forward following additional border measures, which posed significant crew logistics and operational challenges.

"This is a rapidly evolving situation and we thank customers for their patience and understanding at this challenging time," Morgan said.

Air New Zealand general manager cabin crew Leeanne Langridge said these were unprecedented times for the airline and the past few weeks had been unsettling for many staff.

"The increasing travel restrictions due to Covid-19 are having a significant impact on bookings and flight cancellations. While this is a tough decision, it's important we take action now to responsibly manage Air New Zealand through this difficult period to maintain a national airline that is fit for the future."

The London-based cabin crew had always gone "above and beyond", she said.

"Our priority now is supporting our people and we'll be working closely with them and their union."