Why 9/11 victims' names are missing from federal death registry

there were special circumstances that prevented the 9/11 deaths from getting into the Death Master File.

"In most cases there were no physical remains, so (private) funeral directors were not involved," said Steven Schwartz, vital-records registrar for New York City.

Another major non-government source of death reports are family members who are eligible to receive Social Security survivor benefits

via standard.net

We've always said that the Death Master File is not a complete record of all deaths," said Social Security spokesman Mark Hinkle. "It is only an extract of information in our records.