The Federal Aviation Administration’s decree will take effect in two years and apply to new deliveries of airliners.
It will not apply to airlines from other countries that fly into the US but the innovation is likely to be offered to all airlines by manufacturers and could see wider adoption.
The new safety measure is designed to provide extra security when the cockpit door is opened in flight, for example to serve food, or when pilots take rest breaks.
The FAA said the design must “delay a person attempting to access the flightdeck by at least the time required for a crew member to open and reclose the flightdeck door, but no less than five seconds”.
The extra cost is estimated at around $35,000 per aircraft and will affect 121 airlines.
