Transportation and aviation safety officials will make the announcement at a Virginia facility that holds the partially reconstructed jumbo jet that was destroyed on a flight from New York to Paris in July 1996, killing all 230 people aboard.
The National Transportation Safety Board (NTSB) concluded an electrical short likely ignited vapors inside the jetliner's mammoth center fuel tank shortly after takeoff from John F. Kennedy airport.
Fuel tank explosions are extremely rare but there have been a few other known examples worldwide that occurred when planes were on the ground.
Boeing and Europe's Airbus (EAD.PA: Quote, Profile, Research, Stock Buzz) are the world's largest commercial aircraft manufacturers.
Details of the updated measure were not disclosed ahead of the announcement and Transportation Department and FAA officials declined comment.
The Federal Aviation Administration (FAA) proposed a plan in 2005 to retrofit more than 3,000 jetliners with a fuel tank safety device over a period of several years. Airlines balked at the expense estimated in excess of several hundred million dollars.
The new plan is expected to cover fewer planes and carriers are expected to again raise cost concerns.
"I'm pleased it's finally happening but I'm disappointed that it took so long," said Jim Hall, chairman of the safety board at the time of the disaster. "The good news is that the issue of explosive vapors is being addressed."
Hall, who has worked with families of TWA Flight 800 victims to press for action, said he had not been briefed on the Transportation Department's plan.
Congress has recently pressed for action on the measure as has the safety board.
Domestic airlines are taking delivery of few aircraft now due to severe financial constraints caused by skyrocketing jet fuel prices. Airlines are also grounding older, less efficient planes to save on fuel. Industry experts do not expect those aircraft to ever fly again for U.S. airlines.
The FAA has spent years on regulation aimed mostly at trying to reduce the risk of electrical shorts. (Reporting by John Crawley; editing by Carol Bishopric)