The FAA issued a final rule that requires all new commercial airliners to have systems that significantly reduce the risk of center fuel tank fires and those that were built after 1991 to be retrofitted. Although the November 2005 NPRM would have included some transport-category aircraft operated under Part 91, the final rule does not. The new rule was prompted by the July 17, 1996, crash of a TWA Boeing 747 off Long Island with the loss of all 230 aboard. The NTSB eventually determined that the center fuel tank, which contained only vapors, exploded in flight. Transportation Secretary Mary Peters said the cost for installing the new technology will range from $92,000 to $311,000 per aircraft, depending on size.