The FBI has held them for months, and no one seems to know what should be done with them. It's a politically and emotionally charged question for the government, which eventually must decide how to dispose of some of the most despised men in American history.
"I think in Islam, you're supposed to be buried whole, so I would take them and scatter them all over the place," said Donn Marshall, whose wife, Shelley, died at the Pentagon. "They don't deserve any kind of religious courtesies."
In New York, where the monumental task of identifying the remains of 2,823 victims believed to be dead continues, no remains have been linked to the 10 hijackers who crashed two airliners into the World Trade Center. About half the victims' families still are waiting for their loved ones to be identified, though it's likely many never will be because so much of the site was incinerated.
In contrast, the remains of all 40 victims in the Pennsylvania crash and all but five of the 184 victims at the Pentagon site were identified months ago.
A group memorial service is planned for Arlington National Cemetery on Sept. 12, when all the remains from the Pentagon that could not be matched with a particular victim will be buried, said Maj. Sandy Troeber, a spokeswoman.
Little attention has been paid to the terrorists' remains found mingled with those of the Pennsylvania and Pentagon victims.
"It's a unique situation," said Dr. Jerry Spencer, a former chief medical examiner for the Armed Forces Institute of Pathology, who worked 30 years as a Navy forensic pathologist. "The terrorists are usually not in our possession in the United States like this. The other issue is, will the families want them back?"
Four sets of remains in Pennsylvania and five at the Pentagon were grouped together as the hijackers - but not identified by name - through a process of elimination.
Families of the airplanes' passengers and crews and those who died within the Pentagon provided DNA samples, typically on toothbrushes or hairbrushes, to aid with identification. The remains that didn't match any of the samples were ruled to be the terrorists, said Chris Kelly, spokesman for the Armed Forces Institute of Pathology, which did the DNA work. The nine sets of remains matched the number of hijackers believed to be on the two planes.
Without reference samples from the hijackers' personal effects or from their immediate families to compare with the recovered DNA, the remains could not be matched to individuals.
With the one-year anniversary approaching, State Department officials say they have received no requests for the remains. The department would be responsible for handling such a request from any government seeking the return of a citizen's body.
Officials have said that all but one of the nine hijackers recovered had connections to Saudi Arabia. The other was Lebanese.
Officials at the Saudi Embassy in Washington did not respond to requests for comment.
In more typical cases, foreign families also could contact local authorities. But the hijackers' remains are under the control of the FBI.
"To the best of my knowledge, there haven't been any friends or family members to try to claim the remains of these people," said Jeff Killeen, spokesman for the FBI field office in Pittsburgh. "They are in the custody of the FBI in Washington. They have not been released."
In cases where badly damaged bodies cannot be identified, or when no one steps forward to claim a body, state or local laws usually dictate what will be done with them.
"If it's a mass disaster, and they can't identify the remains, they may put all of them in a mass grave or they may be cremated," said Michael Bell, vice president of the National Association of Medical Examiners and the deputy chief examiner for Broward County, Fla.
Authorities usually retain only small DNA samples, photographs or other pertinent information that might lead to identification later or become evidence in a criminal case.
The remains linked to terrorists were taken by the FBI in February, she said.
James Starrs, a professor of forensic science and law at George Washington University, said there should be public oversight of what the government does with human remains, whether they are criminals or victims.
Policies must take into account that there are cases where relatives don't seek repatriation of remains, including many examples of Americans killed on overseas battlefields, noted Starrs, who is known for his forensic work in historical cases, such as the outlaw Jesse James and the mystery of the Boston Strangler.
"Good persons or bad persons, you can't assume that the relatives are going to come to the fore and try to reclaim their remains," Starr said.
The Sept. 12 ceremony at Arlington National Cemetery will hold special significance for families of five people whose remains have never been identified, Col. Jody Draves, a spokeswoman for the Military District of Washington, which oversees the cemetery, said Friday.
The service will include burial of the cremated ashes of all remains not linked to a particular victim, as well as some remains which were identified that family members asked to be included.
"The intent is not as a memorial service but as a group burial for victims not identified," Draves said.