While the exemption for sales of aircraft parts and equipment to entities described in North American Industry Classification System Code 336411 (Aircraft Manufacturing) or 336412 (Aircraft Engine and Engine Parts Manufacturing) was amended to limit the period from July 1, 2008 to September 30, 2008, the exemption was also amended to include sales of parts and equipment for installation in an aircraft operated by a common carrier in interstate or foreign commerce. A refund may be claimed before September 30, 2011 for sales made on or after July 1, 2008 but on or before September 30, 2008 provided the exemption had not already been claimed. Effective October 1, 2008, the exemption on sales of aircraft parts and equipment will extend beyond those entities described in codes 336411 and 336412. ( H.B. 2001, Laws 2008, Second Special Session, effective September 29, 2008, operative retrospectively to July 1, 2008)