Officials are looking into how a New Zealand-designed plane ended up in North Korea, Prime Minister John Key says.

Photo: Screenshot / Pacific Aerospace

The plane, a P-750 XSTOL manufactured by Pacific Aerospace, was sold to China but was spotted last week by the Aviation Week website at North Korea's first airshow.

Mr Key said it would concern him if the plane was exported there in some way because New Zealand has a ban on exports to North Korea.

He said the Ministry of Foreign Affairs and Trade (MFAT) was getting advice on exactly how the plane got there, under what conditions and how long it had been there for.

"New Zealand certainly [directly] selling things to North Korea would be in breach of our sanctions, and we don't try and sell things to a third party to get into a country where we have sanctions, because that breaches the moral code of what we are doing.

"The question is whether we even understood how it was getting there, what took place and those are the facts that MFAT are identifying at the moment."

In April 2014, on a visit to China, Mr Key signed the $75 million agreement between Pacific Aerospace and Beijing General Aviation.

In November that year, Pacific Aerospace delivered the first two planes and agreed to start building the New Zealand-designed P750-XSTOL in China.

The planes, which are designed for extremely short take-off and landings, sell for between $2.3m and $3.1m depending on their size.