The UN's eyes: French Navy enforces North Korea sanctions

Flying above the Yellow Sea between Korea and China, a French naval crew scans the ocean surface for signs of contraband headed for North Korea.

The team is part of an international mission enforcing United Nations sanctions on Pyongyang, flying surveillance trips from the US Futenma base in Japan's Okinawa.

"The UN sends us information on vessels suspected of illicit behaviour," and then a flight plan is drawn up, explained Guillaume, the lieutenant commander who leads the team and can only be identified by his first name.

On board their Falcon 200 aircraft, the team of six uses radar as well as ships' AIS -- the automatic identification system that transmits information including a vessel's identity and its route.

But their best tool remains visual observation: two crew members sit next to the plane's windows, scanning the ocean surface with binoculars and taking photographs.

"We're the eyes of the United Nations in the area," said Guillaume.

Suddenly, the team is on alert: a ship has been spotted with its AIS deactivated, a move considered suspect behaviour.

The pilots reroute the plane, making two passes at an altitude of less than 150 metres (500 feet), looking for the boat's name on its stern and trying to establish radio contact with its crew.

Briefing the team before the flight, Guillaume stressed the importance of a "cordial and professional response" in instances of suspicious behaviour.

"In the context of the international tensions in the area, the goal is to avoid poisoning the situation. We have to be firm but courteous."