14 CFR §450.151

1. (a)General. For any launch or reentry, an operator must document and implement rest requirements that ensure safety-critical personnel are physically and mentally capable of performing all assigned tasks.
2. (b)Work shifts and deviation approval process. An operator's rest requirements must address the following:
   1. (1)Duration of each work shift and the process for extending this shift, including the maximum allowable length of any extension;
   2. (2)Number of consecutive work shift days allowed before rest is required;
   3. (3)Minimum rest period required—
      1. (i)Between each work shift, including the period of rest required immediately before the flight countdown work shift; and
      2. (ii)After the maximum number of work shift days allowed; and
   4. (4)Approval process for any deviation from the rest requirements.
3. (c)Application requirement. An applicant must submit rest rules that demonstrate compliance with the requirements of this section.