North Korea’s state airline Air Koryo resumed flying to Kuwait City on Tuesday, data published by Flightradar 24 has shown.

Following a refuelling pause at Pakistan’s Islamabad International Airport, an Air Koyro Tupolev TU 204-300 arrived in Kuwait City on Tuesday, the data showed.

Flight tracking data showed that as of Thursday, the Air Koryo plane was scheduled to fly back to North Korea at 16:01 local time, on a route that may include a stop-off in Pakistan.

“These passenger services take-on fuel in Islamabad before continuing to Kuwait through Pakistani and Iranian airspace,” a North Korea aviation expert who requested anonymity told NK News on Thursday.

IRREGULAR SCHEDULE AND PURPOSES?

Although the airline started “weekly” Kuwait City flights in early 2011, the unofficial Air Koryo Facebook page said the most recent flights there occurred during a two week window in December 2013.

Reports previously suggested the Pyongyang – Kuwait route was created to shuttle North Korean construction workers to and from contracts in the Middle East. A 2011 Korea Trade Investment Promotion Agency (KOTRA) report said that approximately 3,000 North Koreans were working on construction projects in Kuwait, mostly “unskilled laborers at construction sites earning low wages.”

But North Korean flights to the Middle East have previously raised suspicions in some quarters, with Iraq denying permission to a North Korean overflight request to Syria in 2012 due to fears it could be carrying weapons for Damascus.

And the Air Koryo Pyongyang – Kuwait refuelling point at Pakistan – a country where DPRK diplomats were in 2013 accused of illegally selling alcohol imported in diplomatic pouches – has raised suspicions that the flight route could be used to break UN sanctions.

“North Korea is known to have used commercial and charter aircraft to transport illegal goods — particularly higher-value commodities — in the past,” said Andrea Berger, a North Korea researcher at London’s Royal United Services Institute (RUSI).

• INVESTIGATION: Why is tracking North Korean aircraft so difficult?

“UN Security Council Resolution 2094 (2013) urged states to exercise increased vigilance over North Korean aircraft in recognition of this potential proliferation pathway. North Korean aircraft refuelling in states of traditional proliferation concern should therefore be no exception,” Berger added.

Mark Fitzpatrick, Director of the Non-Proliferation and Disarmament Programme at London’s International Institute for Strategic Studies said that while the Air Koryo route could be of concern, there was no current sign of serious illicit activities with Pakistan.

“[The] use of Air Koryo is one of North Korea’s most reliable means of transporting illicit goods….[but] there has been no sign of nuclear trade between North Korea and Pakistan for over ten years, ever since the black market network led by A.Q. Khan was put put out of business.

“And Kuwait is not known to be a customer of North Korean illicit trade either,” Fitzpatrick added.

The route, which is the longest scheduled Air Koryo service, is not currently offered on the airlines’ official website and has a somewhat erratic service record. And when Air Koryo’s Kuwait ticket office was called Thursday by NK News, a recorded message said the line was out of service.

In November 2011 it was reported that Air Koryo had abruptly cancelled the Pyongyang – Kuwait City route, possibly because of fears that news about the Arab Spring would spread to North Korea.