2 C.F.R. § 200.475 – Travel costs.

(a) General. Travel costs include the transportation, lodging, subsistence, and related items incurred by employees who are in travel status on official business of the recipient or subrecipient. These costs may be charged on an actual cost basis, on a per diem or mileage basis, or on a combination of the two, provided the method used is applied to an entire trip and not to selected days of the trip. The method used must be consistent with those normally allowed in like circumstances in the recipient's or subrecipient's other activities and in accordance with the recipient's or subrecipient's established written policies. Notwithstanding the provisions of § 200.444, travel costs of officials covered by that section are allowable with the prior written approval of the Federal agency or pass-through entity when they are specifically related to the Federal award.
(b) Lodging and subsistence. Costs incurred by employees and officers for travel, including costs of lodging, other subsistence, and incidental expenses, must be considered reasonable and otherwise allowable only to the extent such costs do not exceed charges normally allowed by the recipient or subrecipient in its regular operations as the result of the recipient's or subrecipient's established written policy. In addition, if these costs are charged directly to the Federal award documentation must justify that:
1. (1) Participation of the individual is necessary for the Federal award; and
2. (2) The costs are reasonable and consistent with the recipient's or subrecipient's established written policy.
(c) Dependents.
1. (1) Temporary dependent care costs (dependent is defined in 26 U.S.C. 152) above and beyond regular dependent care are allowable provided that these costs:
  1. (i) Are a direct result of the individual's travel to a conference for the Federal award;
  2. (ii) Are consistent with the recipient's or subrecipient's established written policy for all travel; and
  3. (iii) Are only temporary during the travel period.
2. (2) Travel costs for dependents are unallowable, except for travel of six months or more with prior approval of the Federal agency. See § 200.432.
(d) Establishing rates and amounts. In the absence of an established written policy regarding travel costs, the rates and amounts established under 5 U.S.C. 5701-11 (“Travel and Subsistence Expenses; Mileage Allowances”), by the Administrator of General Services, or by the President (or their designee) pursuant to any provisions of such subchapter must apply to travel under Federal awards (48 CFR 31.205-46(a)).
(e) Commercial air travel.
1. (1) Airfare costs in excess of the basic least expensive unrestricted accommodations class offered by commercial airlines are unallowable except when such accommodations would:
  1. (i) Require circuitous routing;
  2. (ii) Require travel during unreasonable hours;
  3. (iii) Excessively prolong travel;
  4. (iv) Result in additional costs that would offset the transportation savings; or
  5. (v) Offer accommodations not reasonably adequate for the traveler's medical needs. The recipient or subrecipient must justify and document these conditions on a case-by-case basis for the use of first-class or business-class airfare to be allowable in such cases.
2. (2) Unless a pattern of avoidance is detected, the Federal Government will generally not question a recipient's or subrecipient's determinations that customary standard airfare or other discount airfare is unavailable for specific trips if the recipient or subrecipient can demonstrate that such airfare was not available in the specific case.
(f) Air travel by other than commercial carrier. Travel costs by recipient or subrecipient-owned, -leased, or -chartered aircraft include the cost of the lease, charter, operation (including personnel costs), maintenance, depreciation, insurance, and other related costs. The portion of these costs that exceeds the cost of airfare, as provided for in paragraph (d), is unallowable.