As the halls of Congress rattled last week with arguments over wiretaps and torture and what went wrong with intelligence on Iraq, Dan Coleman was thinking of how the next hijacked plane will fly right into the Capitol building.

Five Septembers ago, Coleman, then the FBI’s top expert on Osama bin Laden, was desperately wondering where al Qaeda operatives were hiding.

The answers came out of a clear blue sky.

Today, Coleman’s big, sad eyes still seem to have images of bin Laden imprinted on them.

Retired from the FBI after nearly 30 years in 2004, he is still obsessed with the al Qaeda leader. And he is certain that Washington remains bin Laden’s unfinished business.

Coleman can see the next hijacked plane swooping down over the Mall’s ribbon of green grass and roaring over the tourists’ heads, straight into the Capitol.

Airliners rest virtually unguarded while they are refueled on airport tarmacs, he points out. The Transportation Worker Identification Credential is still far off. Terrorists can easily beat X-ray scanners and explosives detectors, he maintains, especially in Europe.

And it would not be too difficult for al Qaeda operatives, using false identities, to charter a single large airplane, take over the crew and fly it into the Capitol Building loaded with fuel.

“They have to up the ante, make it worth their while” to risk another attack in the United States, Coleman said. “They have to kill a whole lot of people.”

But casualties, he added, “are not so important as burning down the building. And it will burn.”

The FBI said Friday it had “no specific or credible information to suggest that an attack is likely within the U.S. on or around September 11.”

But Coleman said that doesn’t mean much.

“We never heard anything about the last one coming, too.” The CIA’s now-infamous Aug. 2001 warning to the White House that bin Laden was “determined to strike in the U.S,” possibly with aircraft, didn’t offer times, places, names — or the suspects would have been arrested.

Another attack is coming, perhaps soon, says Coleman, now working as a senior adviser to a Tyson’s Corner security software firm called, aptly enough, Harbinger Technologies.

His erstwhile counterterrorism sidekick Michael Scheuer thinks the same. Scheuer headed the CIA’s bin Laden unit until he “burned out,” according to a vivid account in Lawrence Wright’s “The Looming Tower.” He attracted the attention of the Beltway security crowd last week when he took another look at the al Qaeda videotape of Sept. 2., which he found pregnant with warnings that a very big attack is in the offing.

The key: an offer from al Qaeda to Americans to convert to Islam. Most analysts had dismissed it as “conciliatory,” Scheuer says, but they missed the point.

A key prescription of the Koran says Muslims must offer their enemies a chance at conversion — before killing them.

The videotaped message was delivered in unaccented English by “Azzam the American” (Azzam al-Amriki), the U.S. citizen formerly known as Adam Gadahn, who grew up Jewish in the suburbs of Southern California.

Gadahn was introduced on the tape by bin Laden’s Egyptian deputy, the portly surgeon-turned-holy warrior Ayman al-Zawahiri.

Gadahn’s plea to convert was accompanied by the phrase, “before it is too late,” Scheuer pointed out on the Web site of the Jamestown Foundation, a nonpartisan forum favored by former military and intelligence officials.

It signalled the last signal before an attack.

“There are three such actions: multiple, clear warnings of an intention to attack; offers of a truce; and public calls on the foe to convert to Islam,” Scheuer wrote.

“The September 2 video is in no way an isolated occurrence, but rather part of an al-Qaeda effort that began early in 2002 in which bin Laden and al-Zawahiri have more than adequately fulfilled the Prophet Muhammad’s requirements for actions that must be taken vis-à-vis an enemy before attacking him militarily.”

All have been met now, Scheuer wrote, through a series of messages from bin Laden’s lair in the caves of the Pakistan-Afghanistan border.

Taken in context with other al Qaeda taped messages, as well as bin Laden’s discomfort at the dramatic ascendancy of his rival Hezbollah, who fought Israel to a draw in Lebanon — the latest statement is particularly worrisome, he said.

The message is that “there is a dark, pitiable fate awaiting Americans because of their policies and actions toward Muslims.” The California-raised jihadist looks into the camera and says, “Time is running out, so make the right choice before it is too late and you meet the death [that was] the most dismal fate of thousands before you.”

Under the Capitol dome, meanwhile, time seemed to stand still, with Republicans and Democrats in full-throated battle with each other over the mistakes of the past — as with every year since Sept. 2001.

The partisan snarling over the Senate Intelligence Committee’s reports on how President Bush led the nation to the war in Iraq drowned out any thoughtful expressions of how the mistakes of the past could be used to fix the urgent problems of the present — starting with the rapidly deteriorating situations in Afghanistan and Iraq and the escalation of terrorist plots in Europe.

On the House side, Rep. Ed Royce, chairman of a Judiciary Subcommittee, even reopened a debate that was thought finished with the last Congress’ intelligence reform legislation.

Royce said he was so unhappy with the FBI it was time “ to restart the debate over the creation of a domestic intelligence service without police powers, similar to the British MI5.”

In Congress, everybody seems to be looking back to the future.

And so is Osama bin Laden, say those who spent years studying and failing to catch him.

Jeff Stein can be reached at jstein@cq.com.