One of the tragic flaws of 9/11 is now fixed.

President Joe Biden has signed into law the “FAA Reauthorization Act of 2024,” requiring secondary cockpit barriers on all commercial airplanes.

As the Herald reported, the new rule was adopted by the U.S. House 387–26 this week, placing the matter before the president. Now it is the law until 2028 and “reauthorizes the National Transportation Safety Board” to keep it going.

Upgrading all the nation’s airplanes will take time, though.

“The one shortcoming is the 5 to 6 years it will take to implement. Until the retrofitting is completed, we’ll still be vulnerable to a 9/11 style attack,” Brian Sullivan, a retired FAA investigator from Massachusetts, told the Herald Saturday.

The installation of secondary cockpit barriers on all commercial passenger flights is the only 9/11 Commission recommendation that has not been implemented.

Advocates have been pushing for secondary cockpit barriers for decades, saying they’re key to preventing the hijacking of airplanes and keeping terrorists out of the cockpit.

On 9/11, terrorists stormed the cockpit knowing that the doors would be opened early in the flight.

Flight 175 and American Airlines Flight 11 both left Logan Airport on 9/11 with hijackers on board. The two other hijacked jets, Flights 77 and 93, left from DC and Newark, respectively.

U.S. Reps. Brian Fitzpatrick and Josh Gottheimer have been pushing for the secondary cockpit barriers. Massachusetts Congressman Stephen Lynch was also backing the aviation safety act.

A mid-air attack last year on a flight to Boston Logan International Airport showed the continued need for a secondary cockpit barrier on all commercial aircrafts, according to advocates.

Federal authorities said Massachusetts man Francisco Torres tried to open the plane’s emergency exit and then attempted to stab a flight attendant with a broken spoon. Torres in a video was seen moving toward the cockpit as he allegedly attacked the flight attendant.

Passengers, including a former Boston bouncer, ended up tackling Torres and restraining him.