9/11 Families Furious Over Plea Deal For Alleged Terrorists, Wanted Trial

Americans who lost family members in the 9/11 attacks are feeling betrayed by their own government because of a plea deal for the accused terrorists ... a total slap in the face, so says a prominent victim organization.

Brett Eagleson -- the president of 9/11 Justice, an organization representing 9/11 survivors and relatives of victims -- tells TMZ ... the feds did not loop them in or consult them before the shocking pre-trial agreement, and he says it's upsetting for a number of reasons.

For Brett, who lost his father in the terrorist attack 23 years ago, the deal is absolutely awful for these 9/11 families ... whom he says wanted to see the accused face the music in court.

Instead of a lengthy death penalty trial, alleged 9/11 mastermind Khalid Shaikh Mohammed and two of his alleged accomplices -- Walid Muhammad Salih Mubarak bin Attash and Mustafa Ahmed Adam al-Hawsawi -- agreed to plead guilty to conspiracy charges and serve life sentences. Now, they'll just rot away in prison until they die naturally.

But, Brett says 9/11 victims' families had been against the deal from the jump ... they say the absence of a trial prevents them from getting answers and holding the men, and Saudi Arabia, accountable ... a separate battle Brett and co. have been waging in court.

The Pentagon, Department of Defense, federal prosecutors and presidents from both sides of the aisle are drawing Brett's ire here ... he says it's been a total letdown from all branches and forms of government -- and if you listen to his rationale, he certainly has a point.