The Air Force awarded Boeing [BA] a $4 billion contract modification for 68 kits to convert F-15s to the F-15SA variant for Saudi Arabia, according to a Nov. 2 Defense Department statement.

The firm-fixed-price, cost-plus-fixed-fee and cost reimbursable no fee contract modification is for Country Standard Time Compliance Technical Order (CSTCTO) development, integration, testing and fabrication of trial kits to support validation and verification activities. Boeing spokeswoman Lori Moore said recently CSTCTO is the formal Retrofit Engineering Package that controls the incorporation of the modification.

The contract modification also includes the installation of four base stand-up kits, which Moore said are the parts required to establish the inventory depth of spares and support equipment needed to support operating bases. Moore deferred questions to the Air Force regarding when it expected the F-15SA conversions to begin.

F-15SA conversion work is expected to wrap up by Oct. 31, 2013.

This is the second Defense Department contract award to Boeing in five months for F-15SA conversion kits. The Air Force awarded Boeing a $1.8 billion contract June 26 for 68 F-15SA conversion kits. Those conversion kits included wings, tail booms, forward fuselages and other supplies.

Boeing develops the F-15.