Iran just signed the biggest business deal with an American company since 1979

Iran has signed a $16.6 billion deal with the Boeing Company. This is the country's largest deal with a United States company since the Islamic Revolution in 1979.

But, the deal between the aircraft manufacturer and the Islamic Republic may face upheaval in light of an unfriendly American congress and Donald Trump's imminent ascendancy as president. 

Here's are 5 things to know about the deal and how it could be derailed.

Under the terms of the agreement, Iran Air will purchase 80 Boeing aircraft: 30 737 MAX 8s, 15 777-300ERs and 15 777-9s. 

According to Boeing, the company coordinated closely with the US Government throughout the process. It will continue to follow all license requirements as it moves forward to implement the sales agreement.

Boeing is the nation’s top exporter in terms of the value of the goods it sells. Its aircraft have long been a key piece of American diplomacy.

Taking a tip from the president-elect's own playbook, Boeing has announced the deal by highlighting the number of jobs it will support.

In a press release, the company emphasized that the deal would support tens of thousands of US jobs and "nearly 100,000 US jobs in the US aerospace value stream for the full course of deliveries." It's hoping to shore up popular support for the deal, which might curb efforts by congress and Trump that could block it from moving forward.

The company also pandered to US competitiveness, saying it is "proud to ensure America continues to lead in global aerospace" while continuing to create jobs in the country.

Last year, the US led international efforts to lift some sanctions against Iran if it rolled back its nuclear ambitions. Although many politicians and business leaders applauded the landmark agreement in the west and in Iran, GCC countries, the Israeli government and many American politicians criticized the move.

US President-elect Donald Trump has been one of the most vocal American opponents to the nuclear deal, calling it "the stupidest deal of all time." He has also vowed to tear it up once becoming president.

Since the deal went through, American and international companies like Boeing have moved quickly to enter the Iranian market. In September, Boeing got the green light to move forward with its negotiations with Iran Air. But the company had to wait licenses from the US Treasury Department’s Office of Foreign Assets Control before finalizing any agreement.

At the beginning of December, the US congress passed a bill to extend sanctions on Iran that would expire at the end of the year. While Iran expressed discontent with the move, the Obama administration said the decision would not counter the terms of the nuclear agreement.

"While we do not think that an extension of ISA is necessary, we do not believe that a clean extension would be a violation of the JCPOA (Iran deal)," a senior administration official told Reuters.

Already, some congressmen are expressing their plans to combat the Boeing-Iran deal as well. Representative Peter Roskam from Illinoise, where Boeing is headquartered, plans to oppose the agreement according to his communications director.

"We will aggressively fight this deal in next Congress, though we probably won't even need new legislation to do it," Roskam's communication director said.

In the spring, Roskam and two other representatives sent a letter to Boeing discouraging it from opening business negotiations with Iran.

During his campaign, Trump used the Iran deal as a key criticism of the Obama administration. He also cited Israeli frustration with the deal as reason to object to the deal.

Despite his strong rhetoric against the agreement, other international signatories have voiced skepticism that the US could simply tear it up. The deal took years of negotiations between the US, the UK, France, Iran, China, Russia and Germany. 

Many European nations allied with the US have already begun significant trade with Iran since the agreement went into effect. If Trump backs away from the deal, he risks alienating the US from key allies and from Russia, which he has expressed a desire to reconcile with once he takes office.

At the same time, Trump has appointed a secretary of defense and a national security adviser that both have voiced their criticism of Iran and the deal. But Trump has appeared to take a softer tone since the election, saying he will only reexamine the deal and some parts will be renegotiated.

With regards to Boeing, Trump recently attacked the company for the high price it is charging to upgrade the US president's private jet, Air Force One. He tweeted "Cancel order!"

All things considered, it will be difficult for Trump to counter Boeing's promise to support American jobs. A key pledge during his campaign was to create more jobs and help keep them in the US. Trump's supporters will be expecting results, not canceled business transactions.