Twenty-five years after Sept.11, 2001, families and friends of the nearly 3,000 people killed that day remain dismayed that still no one has been convicted — or even stood trial — for the terror attacks.

Khalid Sheikh Mohammed, the self-proclaimed architect of the deadliest acts of terror on American soil, and four of his alleged al-Qaida cronies remain behind bars at the US naval base in Guantánamo Bay, Cuba.

“So many family members have passed in the past 25 years. How sad that these people didn’t live long enough to see justice served,” Maggie McDonnell-Tiberio, whose emergency service NYPD officer husband Brian McDonnell died in the attacks, told The Post.

“Twenty-five years is too long to wait.”

The case has suffered a massive array of setbacks, including years of recent legal squabbles over a scrapped 2024 plea deal in which Mohammed and two others had agreed to admit their guilt in exchange for dodging the death penalty.

The fifth military judge to hear the case, Lt. Col. Michael Schrama, set a June 2028 trial date last month — then days later threw a potential wrench in the case by ruling that the head plotter’s 2007 confession cannot be used in court because it was tainted by torture.

Relatives of the people killed on that fateful day — including more than 400 heroic first responders — are feeling both anguish and outrage as they continue their absurdly long wait for justice.

“It is unconscionable that 25 years later, there still has not been a trial, and we have to wait another two years,” Carol D’Allara, whose husband, NYPD officer John D’Allara, died on 9/11, told The Post.

“Who knows if it’ll even happen then, since they’ve already changed the date numerous times.”

McDonnell-Tiberio said that 25 years “seems like a lifetime ago.”

“With the anniversary, there are so many videos popping up again. Every time I see a video of the towers collapsing, I imagine Brian falling to his death,” she said.

The marathon of delays started soon after Mohammed and four other men accused of aiding the 19 terrorists who hijacked and crashed commercial planes into the World Trade Center, the Pentagon and a Pennsylvania field were captured in Pakistan in 2002 and 2003.

Rather than be sent to New York to face trial, the prisoners were shipped to a secret network of CIA “black site” lockups — where investigators probed them for information about possible future attacks. Mohammed was waterboarded 183 times, according to the Department of Justice.

He eventually admitted to proposing the plane hijacking plot to Osama bin Laden, and training some of the hijackers.

“I was responsible for the 9/11 operation, from A to Z,” he told his questioners.

The admitted terror fiend also confessed to decapitating Wall Street Journal reporter Daniel Pearl — an atrocity captured on video — and serving a role in other infamous plots.

But with Mohammed’s lawyers challenging the admissibility of the CIA confessions, the FBI sat down with him and his alleged partners-in-crime again in 2007 at Guantánamo, where the self-described 9/11 mastermind again confessed to orchestrating the attacks.

Mohammed and four other men, Walid bin Attash, Ammar al-Baluchi, Ramzi bin al-Shibh and Mustafa al Hawsawi, were finally arraigned in a newly created military court in 2008.

The case took a new, ultimately fruitless direction when President Barack Obama — who’d promised to shut down Guantánamo amid human rights concerns — took office a year later.

Obama’s DOJ proposed putting the accused plotters on trial in Manhattan federal court, where they would have faced a jury of New Yorkers just a short walk away from Ground Zero.

But the plan drew swift outrage from some victims’ families, who slammed the White House for affording accused mass murderers the same legal rights as Americans — and claimed to The Post that Mohammed and his crew members would use the trial as a stage to spew about their beliefs.

“This is insane. They’re going to make a mockery of the whole court system 10 blocks away from the World Trade Center,” said retired firefighter Joe Holland, whose son, Joseph III, a commodities trader, died in the the center’s north tower, at the time. “They’re going to scream for holy war in America.”

The Obama administration scrapped plans for the New York trial in 2011.

The case has since continued to drag amid legal fights over defense lawyers’ requests for evidence, the ongoing spat about how to handle the confessions, as well as two judges retiring.

A 2021 trial date came and went, stalled by disruptions stemming from the COVID-19 pandemic. Bin al-Shibh’s case was separated from the others in 2023 after a judge found him mentally unfit for trial.

With no end in sight, Biden administration officials in 2024 announced a deal to end the years-long delay by having Mohammed and two of his co-defendants plead guilty in order to be spared the death penalty.

Plans were set in motion for a lengthy plea hearing in January 2025, where victims’ families would finally get the chance to confront the plotters in a Guantánamo courtroom.

Some victims’ families welcomed the deal as a way to finally end the case and avoid Mohammed and the others dying in custody with their cases still pending.

But others were distraught, maintaining that only death would be an appropriate punishment for the perpetrators of the heinous attacks.

“I wish those responsible could be handed over to the families of those they murdered. Let us deliver their punishment,” McDonnell-Tiberio said. “Anything less than that is too kind.”

“The death penalty is the most severe punishment and that is what they deserve: the maximum punishment,” added retired NYPD police officer, Jim Smith, whose wife, NYPD officer Moira Smith, died responding to 9/11.

Amid backlash about the plea deal — and just months before the 2024 presidential election — President Joe Biden’s admin abruptly tried to scrap the arrangement, leading to years more of litigation on that issue.

Prosecutors said earlier this month that they were willing to head to trial without Mohammed’s confession, rather than face yet another delay while they contest the judge’s ruling at various appeals courts.

As the years tick by, victims’ families are holding out a glimmer of hope — with a healthy dose of skepticism — to someday see justice.

“I don’t have a strong opinion on the death penalty. As long as the people responsible for these attacks, go away for the rest of their life to a place where they will be treated like prisoners and stop being pampered,” said Janice Tietjen, whose son, Port Authority police officer Kenneth Tietjen, died on 9/11.

“I don’t have a lot of confidence that it will happen in two years.”

Janice and her husband Kenneth have blanketed their Middletown, New Jersey neighborhood with more than 800 posters reminding their neighbors about the shockingly long wait for someone to be criminally convicted for carrying out the most notorious terrorist attacks of all time.

“September 11th, 25 years,” the posters read. “Still no justice.”