Now that the historic Iran nuclear deal has opened Tehran to world markets, the Islamic republic has seen a rapid increase in foreign investment.

On Tuesday, Boeing Co confirmed a landmark deal to sell 100 of its 737 and 777 aircraft to Tehran for roughly $25 billion. This marks the first time the aerospace giant has done business with the Islamic republic since 1979.

Boeing isn’t the only company jumping into the game. According to a new report from The Financial Times measuring foreign direct investment (FDI), Iran is now ranked 12th out of 14 in Middle Eastern nations in terms of foreign investment.

While Tehran’s FDI has been climbing steadily since 2013, the real boom began after the lifting of sanctions in January. The country has gained 22 FDI projects during the first quarter of 2016.

This quarter accounted for 40% of all FDI since 2013.

While Boeing is based in the United States, most foreign investment comes from South Korea and Germany. South Korea-based Pohang Iron and Steel announced plans to invest $1.6 billion in the country.

On July 14, Iran and the P5+1 group, consisting of Russia, the United States, the United Kingdom, France, China, and Germany, signed a historic deal to guarantee the peaceful nature of Tehran’s nuclear activities in exchange for sanctions relief.

Tehran has accused Washington of attempting to discourage foreign companies from investing in the Islamic republic.

“To date, all the Western countries are under the US influence. All of our banking operations do not pass without problems,” Supreme Leader Ayatollah Khamenei said during a March news conference, according to IRINN news agency.

“It is clear that behind all this is the United States, who spoke of lifting sanctions, but lifted them on paper only.”

Even Boing indicated that the new deal was careful to “follow the lead of the US government with regards to working with Iran’s airlines,” adding that, “any and all contracts with Iran’s airlines will be contingent upon US government approval.”

US Representative Rick Larsen (D-WA) said that he intends to scrutinize Boeing’s dealings.

“In the coming days the US government will be taking a hard look at the specifics of the deal, to ensure it is consistent with both US interests and those of our international allies, he said in a statement, “and I’ll be tracking those developments closely.”