14 CFR 25.1541 - General.
(a) The airplane must contain -
(1) The specified markings and placards; and
(2) Any additional information, instrument markings, and placards required for the safe operation if there are unusual design, operating, or handling characteristics.
(b) Each marking and placard prescribed in paragraph (a) of this section -
(1) Must be displayed in a conspicuous place; and
(2) May not be easily erased, disfigured, or obscured.