49 CFR 33.35 - Extension of priority ratings.
(a) A person must use rated orders with suppliers to obtain items or services needed to fill a rated order. The person must use the priority rating indicated on the customer's rated order, except as otherwise provided in this part or as directed by the Department of Transportation. For example, if a person is in receipt of a DO-T1 priority rating for a bus and has several buses in inventory that are in need of repair, that person must use a DO-T1 rated order to obtain the needed bus repairs.
(b) The priority rating must be included on each successive order placed to obtain items or services needed to fill a customer's rated order. This continues from contractor to subcontractor to supplier throughout the entire procurement chain.