14 CFR §125.405

1. (a)The pilot in command of an airplane shall carry in the airplane to its destination the original or a signed copy of the—
   1. (1)Load manifest required by § 125.383;
   2. (2)Flight release;
   3. (3)Airworthiness release; and
   4. (4)Flight plan, including route.
2. (b)If a flight originates at the principal operations base of the certificate holder, it shall retain at that base a signed copy of each document listed in paragraph (a) of this section.
3. (c)Except as provided in paragraph (d) of this section, if a flight originates at a place other than the principal operations base of the certificate holder, the pilot in command (or another person not aboard the airplane who is authorized by the operator) shall, before or immediately after departure of the flight, mail signed copies of the documents listed in paragraph (a) of this section to the principal operations base.
4. (d)If a flight originates at a place other than the principal operations base of the certificate holder and there is at that place a person to manage the flight departure for the operator who does not depart on the airplane, signed copies of the documents listed in paragraph (a) of this section may be retained at that place for not more than 30 days before being sent to the principal operations base of the certificate holder. However, the documents for a particular flight need not be further retained at that place or be sent to the principal operations base, if the originals or other copies of them have been previously returned to the principal operations base.
5. (e)The certificate holder shall:
   1. (1)Identify in its operations manual the person having custody of the copies of documents retained in accordance with paragraph (d) of this section; and
   2. (2)Retain at its principal operations base either the original or a copy of the records required by this section for at least 30 days.