(a) Where, in his discretion, the Secretary finds that good cause has been shown, the Secretary may authorize a refund of collected compensatory charges. For purposes of this section, good cause includes, but is not limited to, an error of fact, a miscalculation, or a determination that an original conclusion of entitlement was insufficient, invalid, erroneous or invalidated by subsequent events.(b) Notwithstanding the provisions of § 91.9(e) the Secretary may suspend for a reasonable time the issuance of a certificate of entitlement upon a showing by a payor of compensatory charges that there is a substantial likelihood that the payor will make a showing of good cause under § 91.13(a) .(c) Notwithstanding the provisions of paragraphs (a) and (b) of this section, the issuance of a certificate of entitlement under § 91.9(e) or the distribution to U.S. flag air carriers of funds collected under this part shall be with prejudice to any claim for refund under this section.