Standard Exchange Scheme exemption shields aviation parts from excess customs duty when valued at agreed standard exchange cost. Exempts aircraft parts imported under the Standard Exchange Scheme from customs duty to the extent that duty exceeds what would be leviable if value were the Standard Exchange Cost plus insurance and freight both ways, subject to conditions: parts not new and being repaired or overhauled; a Standard Exchange Agreement between importer and exporter; importer registration with the Director General of Civil Aviation; finality of Standard Exchange Cost; prohibition on drawback claims; and production of exporter's certificate at clearance.