There are strict United Nations sanctions banning a wide range of exports and services to North Korea in response to its nuclear weapons programme.
Pacific Aerospace chief executive Damian Camp said he was looking for answers.
"We're trying to get some detail on that because that aircraft is owned and operated by a Chinese company."
He said his company had sold the 10-seater plane to the Chinese company, translated as Free Sky, several months ago.
"I'm interested to find out more detail on it - we're going to find out what the detail is there. It's certainly nothing to do with us we've got no involvement with it. We're well aware of the restrictions into that part of the world - we're not interested in cutting across any of those."
Camp said his firm tracked its planes as best as it could and it appeared the Chinese firm had displayed the plane at the show.
An international group that researches North Korea, NK Pro, says the aircraft is the latest addition to North Korea's fleet of small planes sourced from foreign countries.
Popular Mechanics reports that North Korea has historically been incredibly secretive about its military capabilities, including the extent of its air force fleet.
"So it really was a historic occasion when the nation opened up to host its first-ever public air show: the International Friendship Air Festival."
Held last week at the Wonsan Airport on the east coast of the country, the event featured fighter jets, helicopters, hot air balloons, commercial airliners from the country's only airline, Air Koryo.
Aircraft photographed at the event included a Sukhoi Su-25 "Frogfoot" close-air-support jet, a Mikoyan MiG-29 Fulcrum fighter, and U.S.-made MD500D helicopters that were illegally exported to the country in the 1980s
"There was even a Pacific Aerospace PAC P-750 XSTOL turboprop-a surprise considering sanctions prevent the export of such aircraft to North Korea," Popular Mechanics reports.
In 2014 then trade minister Tim Grosser enthused about a deal between Pacific Aerospace and China, worth about $120 million.
Earlier this year Pacific Aerospace won a US$13 million order for five of the hardy P-750 XSTOL skydive aircraft to a Chinese government sports agency.
Earlier this year the New Zealand government backed a UN Security Council resolution which strengthened existing sanctions on North Korea covering weapons of mass destruction, arms and luxury goods, and imposes new economic measures affecting transport, banking, and trade.