On Monday, five American prisoners were flown out of Tehran, Iran in a swap for five Iranian prisoners freed in the U.S. and billions in frozen assets. 

The Biden Administration has issued a blanket waiver, allowing international banks to transfer $6 billion in frozen Iranian oil revenue, out of South Korea to Qatar without the threat of U.S. sanctions. The money has been converted from South Korean Wons to Euros with the intent for Iran to use the money for humanitarian purposes.

Iranian President Ebrahim Rasi told NBC that the money will be used “wherever we need it.”

The deal has been criticized, especially by Republican lawmakers, as they believe it will encourage Iran to take more Americans hostage, saying that the U.S. is essentially paying a ransom.

The exchange is still ongoing, but flight-tracking data analyzed by the Associated Press shows a Qatar Airlines flight that took off from Mehrabad International Airport in Tehran, which has been used for exchanges in the past. The plane is en route to Qatar, where the Americans are expected to board a U.S. government plane back to the States. 

The negotiations regarding the prisoner swap have been ocurring since February. Despite this deal, tension between the U.S. and Iran is expected to remain high — especially over Iran’s nuclear program. 

On Tuesday, the five American prisoners arrived safely back to the U.S. at 5:25 a.m.