(NewYorkPost) -- Two years before the airliner attacks, the Saudi Embassy paid for two Saudi nationals, living undercover in the US as students, to fly from Phoenix to Washington “in a dry run for the 9/11 attacks,” alleges the amended complaint filed on behalf of the families of some 1,400 victims who died in the terrorist attacks 16 years ago.

The court filing provides new details that paint “a pattern of both financial and operational support” for the 9/11 conspiracy from official Saudi sources, lawyers for the plaintiffs say. In fact, the Saudi government may have been involved in underwriting the attacks from the earliest stages — including testing cockpit security.

“We’ve long asserted that there were longstanding and close relationships between al Qaeda and the religious components of the Saudi government,” said Sean Carter, the lead attorney for the 9/11 plaintiffs. “This is further evidence of that.”

Lawyers representing Saudi Arabia last month filed a motion to dismiss the lawsuit, which may finally be headed toward trial now that Congress has cleared diplomatic-immunity hurdles. A Manhattan federal judge has asked the 9/11 plaintiffs, represented by lead law firm Cozen O’Connor, to respond to the motion by November.

Citing FBI documents, the complaint alleges that the Saudi students — Mohammed al-Qudhaeein and Hamdan al-Shalawi — were in fact members of “the Kingdom’s network of agents in the US,” and participated in the terrorist conspiracy.

They had trained at al Qaeda camps in Afghanistan at the same time some of the hijackers were there. And while living in Arizona, they had regular contacts with a Saudi hijacker pilot and a senior al Qaeda leader from Saudi now incarcerated at Gitmo. At least one tried to re-enter the US a month before the attacks as a possible muscle hijacker but was denied admission because he appeared on a terrorist watch list.

Qudhaeein and Shalawi both worked for and received money from the Saudi government, with Qudhaeein employed at the Ministry of Islamic Affairs. Shalawi was also “a longtime employee of the Saudi government.” The pair were in “frequent contact” with Saudi officials while in the US, according to the filings.

During a November 1999 America West flight to Washington, Qudhaeein and Shalawi are reported to have tried multiple times to gain access to the cockpit of the plane in an attempt to test flight-deck security in advance of the hijackings.

“After they boarded the plane in Phoenix, they began asking the flight attendants technical questions about the flight that the flight attendants found suspicious,” according to a summary of the FBI case files.

“When the plane was in flight, al-Qudhaeein asked where the bathroom was; one of the flight attendants pointed him to the back of the plane,” it added. “Nevertheless, al-Qudhaeein went to the front of the plane and attempted on two occasions to enter the cockpit.”

The pilots were so spooked by the Saudi passengers and their aggressive behavior that they made an emergency landing in Ohio. On the ground there, police handcuffed them and took them into custody. Though the FBI later questioned them, it decided not to pursue prosecution.

But after the FBI discovered that a suspect in a counterterrorism investigation in Phoenix was driving Shalawi’s car, the bureau opened a counterterrorism case on Shalawi. Then, in November 2000, the FBI received reporting that Shalawi trained at terrorist camps in Afghanistan and had received explosives training to perform attacks on American targets. The bureau also suspected Qudhaeein was a Saudi intelligence agent, based on his frequent contact with Saudi officials.

More, investigators learned that the two Saudis traveled to Washington to attend a symposium hosted by the Saudi Embassy in collaboration with the Institute for Islamic and Arabic Sciences in America, which was chaired by the Saudi ambassador. Before being shut down for terrorist ties, IIASA employed the late al Qaeda cleric Anwar al-Awlaki as a lecturer. Awlaki ministered to some of the hijackers and helped them obtain housing and IDs.

The FBI also confirmed that Qudhaeein’s and Shalawi’s airline tickets for the pre-9/11 dry run were paid for by the Saudi Embassy.

“The dry run reveals more of the fingerprints of the Saudi government,” said Kristen Breitweiser, one of the New York plaintiffs, whose husband perished at the World Trade Center.

“These guys were Saudi government employees for years and were paid by the Saudi government,” she added. “In fact, the Saudi Embassy paid for their plane tickets for the dry run.”

After the Nov. 19, 1999, incident — which took place less than two months before the first hijackers entered the US — both Saudi men held posts as Saudi government employees at the Imam Muhammad Ibn Saudi Islamic University, the parent of IIASA — “a further indication of their longstanding ties to the Saudi government,” the 9/11 complaint states.

Carter said in an interview that the allegations that the Saudi Embassy sponsored a pre-9/11 dry run — along with charges of other Saudi involvement in the 9/11 plot, from California to Florida — are based on “nearly 5,000 pages of evidence submitted of record and incorporated by reference into the complaint.”

They include “every FBI report that we have been able to obtain,” though hundreds of thousands of pages of government documents related to Saudi terror funding remain secret.

Attempts to reach lawyers representing the Saudi government by phone and email were unsuccessful. However, in last month’s motion to dismiss the lawsuit, they argued that the plaintiffs cannot prove the kingdom or its employees directly supported the hijackers.

(Photo: Getty Images)