WASHINGTON (CNN) -- Nearly 16 years after a fuel tank explosion destroyed TWA Flight 800, killing all 230 aboard, the Federal Aviation Administration on Friday proposed to fine Boeing Co. $13.57 million for failing to meet a deadline intended to prevent similar catastrophes.
The FAA said Boeing failed to meet a 2010 deadline to give airlines information on how to reduce fuel tank flammability, missing the deadline by 301 days for its B-747 aircraft, and by 406 days for its B-757 planes.
Because of the missed deadline, airlines have asked the FAA for extensions to make necessary fixes, the FAA said.
The FAA said it is considering extending a deadline requiring airlines to retrofit half of their aircraft by 2014, but will not extend a 2017 deadline to retrofit all impacted aircraft.
Some 383 Boeing aircraft in the United States are affected by the delays, it said.
"We take this matter very seriously," said acting FAA Administrator Michael Huerta. "We have issued hundreds of directives to eliminate fuel ignition sources over the past 16 years, and this step will add another layer of safety."
In a two-page letter to Boeing on Friday, the FAA proposed the fine of $13,574,400.
Miles Kotay, a Boeing spokesman, said Friday afternoon that the company had just received the information and would comment after it had a chance to review it.
The July 17, 1996, explosion of TWA 800, a Boeing 747, was one of the deadliest accidents in aviation history, and was among the most difficult to solve. Although it was originally feared the explosion over the Atlantic Ocean near Long Island, New York, may have been downed by terrorists, National Transportation Safety Board investigators eventually concluded that a short in some electrical lines ignited the volatile fuel-air mixture in the plane's nearly empty center-wing fuel tank.
The TWA 800 case illustrates the slow process of identifying and correcting dangerous systems on sophisticated aircraft. By the time all jetliners are retrofitted with safety systems in 2017, two decades will have passed since the initial accident.
The FAA has itself come under fire for the slow pace of change. In 2005, the NTSB criticized the FAA, saying there had been little progress in making aircraft safer from fuel tank explosions.
"The stark reality is that on a fleet-wide basis, on the flammability side we are no different today than we were in 1996," the NTSB said at the time.
On Friday, the FAA took the offensive, saying Boeing had failed to meet deadlines.
The FAA said that since the TWA accident, it has issued 283 directives to prevent the ignition of vapors in and around commercial aircraft fuel tanks.
In January 2010, Boeing committed to providing instructions for FAA approval for airline mechanics by December of that year. The instructions were to explain how to install systems that would replace the oxygen in airplane fuel tanks with non-flammable nitrogen gas, reducing the risk of explosion. But it missed those deadlines, the FAA said.
The FAA said Airbus, the other aircraft manufacturer, met the deadline.
Boeing has 30 days to respond to the agency.