"The NTSB conducts very thorough and methodical investigations," Nantel said in a statement.
"The TWA Flight 800 investigation lasted four years and remains one of the NTSB’s most detailed investigations," Nantel continued. "Investigators took great care reviewing, documenting and analyzing facts and data and held a five-day hearing to gather additional facts before determining the probable cause of the accident during a two-day Board meeting."
Nantel said the safety regulation agency's report on the 1996 TWA crash was 400 pages.
She said the NTSB's protocol for dealing with petitions to reopen prior investigations is determining if new or incorrect information has been discovered, and then assigning the case to a related unit within the agency.
The agency said it usually responds to petitions within 60 days.
When TWA Flight 800 crashed in the Atlantic Ocean shortly after taking off from New York's John F. Kennedy International Airport during the 1996 summer Olympics in Atlanta, speculation spread that the plane was either bombed or hit with a surface-to-air missile.
The NTSB's four-year investigation ruled out such external factors, focusing instead on the possibility that an electrical short-circuit caused the explosion of the 747 airplane.
The agency said its reports on the TWA Flight 800 crash have "been available to the public since the late-1990s" and "contains more than 17,000 pages of supporting material."