Typical jump plane modifications include in-flight doors, deflectors, steps and rails. Modifications that are not specifically described in the Aircraft Flight Manual must be accomplished by FAA issuance of either a Supplemental Type Certificate (STC) or a Field Approval. For $100 ($200 for non-USPA members, USPA sells STCs for jump conversions of Cessna 170, 172, 180, and 182 aircraft. E-mail the Government Relations department at GovRelations@uspa.org or call (540) 604-9740.