It will cost the airline industry an estimated $256 million to upgrade the "black box" recorders, according to a Federal Aviation Administration (FAA) estimate.

In a newly proposed FAA rule, the government wants all commercial aircraft modified within four year to have new voice recorders that record the last two hours of cockpit audio instead of the last 15 to 30 minutes. In addition, an improved data recording system would be requires to have the last 25 flight hours recorded.

Independent power systems must be installed to provide each recording system with 10 minutes of back-up power.

The proposed rule gives aircraft manufacturers two years to implement the upgrades on new aircraft. The rule would apply to all aircraft capable of carrying more than 10 passengers.

The FAA has posted further information on its Web site at http://www.faa.gov/avr/arm/nprm.cfm?nav=nprm.