FBI documents later cited in legal filings allege that in 1999, the Saudi embassy in Washington, DC funded a “dry run” of the 9/11 attacks. Two Saudi nationals, posing as students, were paid to fly from Phoenix to Washington, DC and attempt to access a cockpit, supposedly as part of research into flight deck security. This caused an emergency landing in Ohio and triggered an FBI interrogation, although the men were released shortly after.

The same lawsuit claims the men were part of a broader network of Saudi agents operating in the U.S., trained in Afghanistan, and connected to other al-Qaeda operatives involved in the 9/11 attacks. One of the students was allegedly employed by Saudi Arabia’s Ministry of Islamic Affairs.

According to a 2012 FBI update and 9/11 Commission testimony, two of the 9/11 hijackers arrived in Los Angeles in January 2000 and were allegedly helped by Saudi officials. A Saudi diplomat, a Ministry of Islamic Affairs official, and a radical cleric in Los Angeles were suspected of providing housing, financial aid, and logistical support. One of these officials was later believed to have reported to the Saudi ambassador and oversaw employees of Saudi-funded mosques.

In April 2016, former members of Congress who co-chaired the congressional inquiry into the 9/11 attacks revealed to CBS News that the still-classified “28 pages” of the congressional report contained potential evidence of Saudi Arabia’s substantial involvement in the attacks. This renewed public and legislative calls to release the documents.

In May 2016, Congress passed the Justice Against Sponsors of Terrorism Act (JASTA). The law amended the Foreign Sovereign Immunities Act and the Anti-Terrorism and Effective Death Penalty Act, allowing U.S. citizens to sue foreign states for injuries or deaths caused by acts of international terrorism on U.S. soil.

The practical impact was to open the door for 9/11 victims and families to pursue civil litigation against Saudi Arabia for its alleged role in supporting the attacks.

On March 20, 2017, 1,500 injured survivors and 850 family members of 9/11 victims filed a lawsuit against the Kingdom of Saudi Arabia. The plaintiffs alleged that Saudi officials and employees had prior knowledge of al-Qaeda’s plans and "knowingly provided material support and resources" to the terrorist group. This included claims that some officials were al-Qaeda operatives or sympathizers.

On March 2, 2020, the plaintiffs filed a letter in court stating that potential witnesses in the lawsuit had received threats. Saudi Arabia requested the court to disclose the identities of these individuals.

In April 2020, the FBI accidentally failed to redact the name of a mid-level Saudi Foreign Ministry official in a court filing. The official had worked at the Saudi Embassy in Washington during 1999–2000 and was allegedly involved in overseeing mosque employees and possibly supporting the 9/11 hijackers. He had previously been identified only in redacted form in FBI records.

A U.S. Magistrate Judge ordered two members of the Saudi royal family to answer questions as part of the ongoing lawsuit. Plaintiffs described the court order as a turning point in the long legal battle to hold Saudi officials accountable.

On the 20th anniversary of the attacks, President Joe Biden ordered the declassification of FBI documents related to 9/11 and potential Saudi involvement. The first documents were released on September 11, 2021, with more to follow over six months.

In response, the Saudi Embassy in Washington, DC issued a statement declaring: “No evidence has ever emerged to indicate that the Saudi government or its officials had previous knowledge of the terrorist attack or were in any way involved in its planning or execution. Any allegation that Saudi Arabia is complicit in the September 11 attacks is categorically false."

In March 2022, the FBI declassified a 510-page report it had originally produced in 2017. The report stated that there was a “50/50 chance” a Saudi official had prior knowledge of the 9/11 attacks, based on his interactions with two Islamist extremists involved in the plot.