Update Nov. 5, 4:30 p.m.: This story has been updated to include language from the nuclear agreement that clarifies the difference between violating the sanctions and violating the nuclear deal itself.

Original story: One of Iran’s commercial airlines last week bought a U.K.-manufactured jet with the aim of using it to deliver Iranian soldiers and weapons to Syria in support of the embattled regime of President Bashar Assad, International Business Times has learned. The purchase of the aircraft by an Iranian concern represents a clear violation of the deal brokered by the administration of U.S. President Barack Obama, under which Iran pledged to scale back its nuclear program in exchange for a lifting of sanctions, said senior American officials and attorneys who handle issues associated with sanctions compliance.

“Temporary sanctions relief ... currently in place does not cover the sale or lease of complete aircraft to Iran,” said Betsy Bourassa, a representative of the Office of Terrorism and Financial Intelligence within the Treasury Department in Washington. And a representative of the State Department told IBT that it was aware of the sale and is investigating the transaction.

Under the terms of the ongoing sanctions, Iran is barred from purchasing aircraft from U.S. and European entities -- and U.S. and European entities are barred from selling them to Iran -- until Tehran has satisfied inspectors with the International Atomic Energy Agency that it has begun rolling back its nuclear program, according to sanctions lawyers at Sheppard Mullin. Calls to Iran’s Foreign Ministry in Tehran were not returned.

Although the nuclear agreement itself does not specifically require Iran to stop purchasing aircraft, it does require that Tehran "refrain from any action inconsistent with the letter, spirit and intent of this JCPOA [Joint Comprehensive Plan of Action, i.e., the nuclear deal] that would undermine its successful implementation." 

A violation of the sanctions could delay the implementation of the nuclear accord, experts told IBT.

“This could affect the way Iranian sanctions are eased,” one attorney said, speaking on condition of anonymity to avoid complicating his clients’ dealings with Iran.

The aircraft purchase marks the second time within five months that the Iranian airline, Mahan Air, one of the country’s largest domestic and international carriers, has purchased aircraft to expand its Tehran-based fleet. Linking Iranian cities to Asian and European destinations, Mahan also flies to Damascus, where it delivers crucial stores of weaponry and troops of the elite ranks of the so-called Quds forces, which are aiding in the defense of the Syrian regime.

Airan1 U.S. Secretary of State John Kerry (left) and the unidentified chief of staff of Iran's Foreign Minister Mohammad Javad Zarif (center) enter the Hotel Bristol in Vienna Oct. 29, 2015. Kerry and other leaders were in Vienna to discuss a resolution of the Syrian Civil War. Photo: Brendan Smialowski/AFP/Getty Images

“Mahan Air’s close coordination with the Quds Force -- secretly ferrying operatives, weapons and funds on its flights -- reveals yet another facet of the Islamic Revolutionary Guard Corps extensive infiltration of Iran’s commercial sector to facilitate its support for terrorism,” David Cohen, the U.S. under secretary for terrorism and financial intelligence, said at a press briefing in Washington in 2011.

Mahan flights take off from Tehran and Abadan, another Iranian city, at unspecified times and without publicizing their destinations. The flights frequently disappear from tracking systems once they enter Syrian airspace. Radar then shows them having landed in Damascus.

The latest aircraft deal was carried out despite American officials’ previous pledges to prevent Mahan from acquiring additional jets and despite the fact that the carrier has been formally blacklisted by U.S. and European authorities for allegedly transporting weapons that facilitate terrorism. Mahan representatives did not return calls.

Aviation records maintained by a private registry show that Mahan purchased the jet from an individual listed as A. Grundlingh Oct. 15. Anton Grundlingh registered the plane in South Africa, where he is the director of three aircraft-affiliated companies and a shareholder in a financial-services firm.

Six months ago, the U.S. Treasury Department took punitive measures against an Iraqi company, Al-Naser Airlines, and a Syrian businessman for selling Boeing aircraft to Mahan. The department froze American-held assets of Al-Naser as well as businessman Issam Shammout and his Sky Blue Bird Aviation firm, banning U.S. entities from conducting business with them. The third party that sold the plane to Mahan most recently could be subject to similar proceedings, as could the plane’s previous owners -- assuming it’s proven they had knowledge of the plane’s final sale to Iran. They could face other civil and even criminal charges. Financial institutions involved in the transaction are also at risk of being blacklisted.

In October 2011, the Treasury Department announced that Mahan would be sanctioned for providing financial, material and technological support to the Quds Force in the Islamic Republic Guard Corps. The airline was also accused of flying Quds Force members linked to a plot to kill Saudi Arabia’s former ambassador to the U.S., Adel al-Jubeir.

Iran US ties Iranian President Hassan Rouhani leaves after delivering a speech at a plenary session during the Asian African Conference in Jakarta, Indonesia, April 22, 2015. Photo: Reuters/Beawiharta

Before Mahan Air purchased the aircraft, several other European airlines owned it, including Malmo Aviation, a Swedish company, and Blue 1, a Finnish firm. Grundlingh bought the plane May 7 from Triangle Regional Aircraft Leasing, previously known as BAE Systems Regional Aircraft Leasing.

Based in the U.K., BAE Systems could be penalized because of the transaction. So could Falko, another leasing company, which purchased BAE Systems Asset Management and its associated aircraft portfolio. Mahan Air is a private Iranian airline, but, due to the fact Iran’s economy is largely controlled by the government, analysts said Tehran officials most likely knew about the transaction and gave it the green light.

“Iran has an extremely old fleet. The average age of their planes is about 19 years. As part of the nuclear deal, Iran wanted the U.S. to make concessions in that sector,” said Alex Vatanka, an expert on Iran with the Middle East Institute think tank in Washington. Vatanka added that there is disagreement within the Iranian government about whether the country should have to wait to make these kinds of purchases.

The jet seats about 80 people and has significant cargo space. It would be capable of transporting not only soldiers but also small arms and anti-tank missiles.

IBT tracked several Mahan Air flights over the span of two days and found at least two flights that took off from Damascus, landing in Al-Hasakah, Syria, the site of intense fighting between the Islamic State group and regime forces and their allies, before flying back to Tehran.

The purchase by Mahan comes at a time when Iran and Russia are intervening militarily in Syria to prop up Assad. For more than a month, Russia has bombed targets where U.S.-armed rebels are stationed. Iran is sending weapons and fighters to expand Hezbollah’s reach on the ground. Combined, Iran and Russia have given Assad the upper hand in the battle against the rebels.

“It is a testament to the changing realities on the ground in Syria,” Vatanka said.

Iranian press reported this week that Nasim Air, a new Iranian airline that is reportedly partially owned by Mahan Air, purchased a Boeing 737.  Nasim Air could not be reached for comment. Should the report prove to be true, the transaction would point to Mahan’s widening operations and its ability to circumvent the law and escalate the violence in Syria.

The U.S. could be doing more to block Iranian aircraft purchases, said Emanuele Ottolenghi of the Foundation for Defense of Democracies, a Washington think tank that is critical of American diplomacy with respect to Iran. The U.S could press for greater financial penalties on those who enable Mahan to acquire planes used in the conflict in Syria, he suggested.

“What the U.S. can do is discourage [companies] from getting involved in these deals by going after [the] whole industry that services Mahan,” Ottolenghi said. “The problem is that all those that have been involved with Mahan before are still there. They are still involved.”