f) Firearms in checked baggage. No aircraft operator may knowingly permit any person to transport in checked baggage:
(1) Any loaded firearm(s).
(2) Any unloaded firearm(s) unless—
(i) The passenger declares to the aircraft operator, either orally or in writing before checking the baggage that any firearm carried in the baggage is unloaded;
(ii) The firearm is carried in a hard-sided container;
(iii) The container in which it is carried is locked, and only the individual checking the baggage retains the key or combination; and
(iv) The checked baggage containing the firearm is carried in an area that is inaccessible to passengers, and is not carried in the flightcrew compartment,.
(3) Any unauthorized explosive or incendiary.
(g) Ammunition. This section does not prohibit the carriage of ammunition in checked baggage or in the same container as a firearm. Title 49 CFR part 175 provides additional requirements governing carriage of ammunition on aircraft.