Federal prosecutors have accused three men tied to Iranian terrorist networks of helping organize a failed attack against RAF Fairford, a United Kingdom military base. One defendant allegedly continued coordinating terrorist activity from a New York jail while awaiting trial on separate terrorism charges.

Mohammad Baqer Saad Dawood al-Saadi, a dual national of Iran and Iraq, allegedly worked with Mohammad Ali al-Hassani and Mohsen Mohajeri, according to a Department of Justice release. Al-Hassani is an Iraqi national, while Mohajeri is an Iranian national.

Prosecutors allege that the three men conspired to commit nearly 20 terrorist attacks and attempted attacks across Europe and the United States. An eight count indictment says the activity was conducted in the name of two terrorist networks aligned with Iran and designated by the United States as Foreign Terrorist Organizations.

“Even after one of their co-conspirators was arrested and placed in federal custody, the defendants allegedly continued coordinating terrorist activity through coded communications and a network of associates overseas,” U.S. Attorney Jamie McDonald for the Southern District of New York said in the release.

McDonald added, “The threat presented by Iran and Iran-backed terrorist groups to America and our allies is not hypothetical — it is very real.” The allegations surrounding RAF Fairford put that warning in stark terms, with prosecutors describing coded messages, overseas contacts, surveillance and preparations involving fuel and vans.

The indictment alleges that al-Hassani managed the September plot targeting RAF Fairford. The base housed U.S. military aircraft and personnel at the time in support of the war in Iran.

Al-Saadi was being held in the Southern District of New York while awaiting trial on pending terrorism charges. Prosecutors say he attempted to communicate with al-Hassani and Mohajeri by sending coded messages through third parties.

Al-Hassani and Mohajeri were both in Iran during the attempted RAF Fairford scheme, according to the statement. The pair allegedly relied on a network of contacts in the United Kingdom to advance the operation.

Al-Saadi was charged in May with collaborating with and working on behalf of the Islamic Revolutionary Guard Corps, other Foreign Terrorist Organizations and Kataib Hezbollah. Prosecutors identify him as a commander of Kataib Hezbollah, an Iraqi militia group backed by the Islamic Revolutionary Guard Corps.

Those earlier charges also accused al-Saadi of participating in the planning and promotion of around 18 terrorist attacks in Europe. He was further charged with attempting to bomb a synagogue in New York.

The indictment alleges that al-Hassani and Mohajeri, who is described as an Islamic Revolutionary Guard Corps operative, worked with al-Saadi to facilitate and complete many of the European attacks. Prosecutors also allege that al-Hassani used contacts and criminal associates to carry out attacks in the United Kingdom.

Al-Saadi was arrested abroad in early May and transferred to U.S. custody for prosecution. He has remained in federal custody since arriving in the United States, and no additional attacks were attributed to the three men during the next four months.

Prosecutors say activity resumed in August, when al-Hassani directed and paid associates in the United Kingdom to take “preparatory steps” for the RAF Fairford plot. Those steps allegedly included conducting surveillance of the base perimeter.

The following month, al-Hassani allegedly paid several people to help prepare the operation. Prosecutors say the preparations included obtaining vans and barrels of fuel, researching chemical accelerants and purchasing items that could be used as explosive shrapnel.

In late September, al-Hassani allegedly instructed individuals to drive three vans toward RAF Fairford, with some of the vehicles carrying barrels of fuel. At least two vans encountered a security roadblock and could not continue to the base.

United Kingdom law enforcement authorities later recovered three white vans and arrested the individuals involved. The attempted operation failed before the vehicles could proceed to RAF Fairford.

Prosecutors also allege that al-Saadi used telephone calls with family members in Iraq to relay coded messages to al-Hassani and Mohajeri in the days before the plot. Three days before the attempted operation, he asked about al-Hassani and told his family to give him money so “we can do it.”

The eight count indictment includes six charges against all three defendants, carrying a total maximum penalty of 90 years in prison or life imprisonment. Two additional charges apply only to al-Saadi, with maximum penalties of 20 years or life in prison.