14 CFR 250.8: Denied boarding compensation.

(a) Every carrier shall tender to a passenger eligible for denied boarding compensation, on the day and place the denied boarding occurs, except as provided in paragraph (b), cash or an immediately negotiable check for the appropriate amount of compensation provided in § 250.5.

(b) Where a carrier arranges, for the passenger's convenience, alternate means of transportation that departs before the payment can be prepared and given to the passenger, tender shall be made by mail or other means within 24 hours after the time the denied boarding occurs.