ds a group of religious extremists gained influence in Saudi Arabia's government and provided aid to the hijackers.

3 The second hijacked plane hits the World Trade Center on Sept. 11, 2001. Tamara Beckwith/NY Post

3 Brett Eagleson, president of 9/11 Justice, called Saudi Arabia's continued denial of responsibility  maddening.  Michael Nagle for NY Post

 Saudi Arabia is a supposed ally and a friend of ours. Friends don't treat friends like that,  added Brett Eagleson, whose father, Bruce, was killed on 9/11.

In total, 2,977 civilians were murdered on Sept. 11, 2001, when 19 al Qaeda terrorists - 15 of whom were Saudi citizens - hijacked four airliners and crashed them into the Twin Towers, the Pentagon and a crash site in Shanksville, Pennsylvania.

The terror group's leader, Osama bin Laden, was a member of one of the kingdom's wealthiest families, although the Saudis yanked his citizenship after he became a vocal critic of both the US and Riyadh.

After years of twists and turns - including an act of Congress making it easier for 9/11 victims' families to sue countries accused of sponsoring terrorism - the case consolidated other suits and sharpened accusations that Saudi officials teamed up with the hijackers who came to the US in early 2000.

Oral arguments are expected to last around 45 minutes Wednesday. The court is then expected to rule in writing on a future date.