Plastic cutlery on some Air New Zealand flights is re-used up to 10 times before being thrown away.

And Qantas makes it last even longer - one of its suppliers reportedly says plastic knives, forks and spoons are being used as many as 30 times.

Qantas disputes that figure but told The Sunday Telegraph in Sydney that utensils could be used at least three times.

"It really depends on how far the cutlery has deteriorated," a spokesman said. "It could be quite a few more times than three."

Air New Zealand said yesterday that plastic dinnerware used on international flights - cutlery, bowls, plates and trays - was sorted by staff for cleaning and reuse. It said there was an environmental benefit in the practice.

Spokesman Mark Street said staff put food waste into bins, then placed trays, plates and cups into trolleys for collection by caterers at international locations for cleaning and reuse.

Items used on international services could not be recycled because of international quarantine and biosecurity laws.

"As plastic items cannot therefore be recycled, we use commercial grade rotable products including bowls, plates, trays and cutlery which is far more environmentally friendly than sending millions of one-use items to landfill each year.

"These items are washed by our catering supplier in commercial dishwashers. Rotatable items generally have a life cycle of around 10 uses, depending on use."

Items were reused until they were found to be damaged or marked.

Items from domestic flights were sorted into waste, recyclable and biodegradable items before being discarded or recycled.

But Penny Tregear, a specialist adviser on food service for the Food Safety Authority said yesterday if cutlery was reused, the business would be responsible for ensuring it was safe.

A Qantas spokesman said: "The wash and re-use of equipment in an airline meal service environment is no different to a restaurant, hotel or other catering provider.