(a) An application for a grant payment is made on FAA Form 5100-6, accompanied by --

(1) A summary of project costs on Form FAA-1630;

(2) A periodic cost estimate on Form FAA-1629 for each contract representing costs for which payment is requested; and

(3) Any supporting information, including appraisals of property interests, that the FAA needs to determine the allowability of any costs for which payment is requested.

(b) Contractor's certifications. Each application that involves work performed by a contractor must contain, in the contractor's certification in the periodic cost estimate, a statement that "there has been full compliance with all labor provisions included in the contract identified above and in all subcontracts made under that contract", and, in the case of a substantial dispute as to the nature of the contractor's or a subcontractor's obligation under the labor provisions of the contract or a subcontract, and additional phrase "except insofar as a substantial dispute exists with respect to these provisions".

(c) If a contractor or subcontractor fails or refuses to comply with the labor provisions of the contract with the sponsor, further grant payments to the sponsor are suspended until the violations stop, until the Administrator determines the allowability of the project costs to which the violations related, or, to the extent that the violations consist of underpayments to labor, until the sponsor furnishes satisfactory assurances to the FAA that restitution has been or will be made to the affected employees.

(d) If, upon final determination of the allowability of all project costs of a project, it is found that the total of grant payments to the sponsor was more than the total United States share of the allowable costs of the project, the sponsor shall promptly return the excess to the FAA.