Customs exemption for aircraft imports carries bond-based IGST liability and re-export and non-sale conditions on importers. The amendment creates an exemption for aircraft, aircraft engines and parts imported under specified Schedule II transactions, granting nil customs duty subject to Condition No. 102. That condition requires the importer to execute a bond to: pay integrated tax on the service element if applicable; refrain from selling or parting with the goods without prior Customs permission; re-export the goods within three months after the supply period; and pay on demand integrated tax that would have been payable in case of non-compliance. The amendment is given retrospective effect with a refund safeguard.