COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 767 Series Aeroplanes AD/B767/56 Vertical Stabiliser 8/91 Applicability: Model 767 series with line numbers 300 through 307. Requirement: Action IAW the Technical Requirements of FAA AD 91-10-09 Amdt 39-6993. Note: Boeing SB 767-55A0007 refers. Compliance: As specified in the Requirement Document. Background: Modification of the vertical stabilizer forward closure rib by installation of a lower plate and a panel assembly over lightening and access holes, was not incorporated during production on certain aircraft.