Not later than 180 days after the date of the enactment of this Act, the Administrator of the Federal Aviation Administration shall issue an order that—
(1)
requires, on each commercial aircraft operating under part 121 of title 14, Code of Federal Regulations, the installation of a barrier, other than the cockpit door, that prevents access to the flight deck of an aircraft; and
(2)
requires, for an aircraft—
(A)
that is equipped with a cockpit door, that the barrier required under paragraph (1) remain locked while—
(i)
the aircraft is in flight; and
(ii)
the cockpit door separating the flight deck and the passenger area is open; and
(B)
that is not equipped with a cockpit door, that the barrier required under paragraph (1) remain locked as determined appropriate by the pilot in command.