A Pennsylvania congressman has introduced a bill that could require airlines to install currently voluntary secondary barriers on thousands of aircraft.
The bill, HR 1775, proposes mandating a wire-mesh door that would be locked in place whenever the reinforced cockpit doors are opened during flight.
The US Federal Aviation Administration (FAA) mandated airlines to install the reinforced cockpit doors after the terrorist attacks on 11 September 2001, but the flight deck still remains vulnerable, says Representative Mike Fitzpatrick.
"The problem is that at some point the pilots need to open the cockpit door to get a meal or rest," he says. "That is the exact moment when terrorists strike."
The concept of a secondary barrier has been proposed for more than a decade. In In the wake of the September 2001 attacks, the International Federation of Air Line Pilots Associations supported a mandate for installing a wire-mesh door as secondary barriers in addition to the reinforced cockpit door.
An RTCA committee set up by the FAA published a document in September 2011 that established standards that allow secondary barriers to comply with airworthiness regulations.
Airlines have been reluctant to embrace the concept despite the enthusiasm shown by pilots unions. United Airlines originally ordered Boeing 787s with secondary barriers, but decided to remove them before the aircraft were even delivered.
Pilots unions objected to United's decision last year, and again last March when the Transportation Security Administration (TSA) planned to allow passengers to carry pocket knives on board commercial aircraft. That measure was supposed to go into effect on 25 April but has been delayed.