(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.