Airfare costs in excess of customary standard commercial airfare (coach or equivalent), federal government contract airfare (where authorized and available), or the lowest commercial discount airfare are unallowable except when such accommodations would:
require circuitous routing;
require travel during unreasonable hours;
excessively prolong travel;
result in additional costs that would offset the transportation savings; or
offer accommodations not reasonably adequate for the traveler's medical needs.
The institution must justify and document these conditions on a case-by-case basis in order for the use of first/business-class airfare to be allowable in such cases.