Except for all-cargo operations as defined in Sec. 110.2 of this chapter, after October 15, 2007, for all passenger carrying airplanes that require a lockable flightdeck door in accordance with Sec. 121.313(f), the certificate holder must have an approved means by which the cabin crew can discreetly notify the flightcrew in the event of suspicious activity or security breaches in the cabin. [Doc. No. FAA-2005-22449, 72 FR 45635, Aug. 15, 2007, as amended by Amdt. 121-353, 76 FR 7488, Feb. 10, 2011]