In 2005, a business case was developed with three options to extend the life of the fleet. The first two options involved expanding the service life extension program (SLEP) at a cost of $4.6 billion and $3.16 billion, respectively. The third option, worth $1.72 billion, was to build 242 new wings and avoid the cost of expanding the SLEP. In 2006, option 3 was chosen and Boeing won the contract. The base contract is for 117 wings with options for 125 additional wings. In 2013, the Air Force exercised a portion of the option to add 56 wings, putting 173 wings on order with options remaining for 69 additional wings. In November 2011, two A-10s flew with the new wings fitted. The new wings improved mission readiness, decreased maintenance costs, and allowed the A-10 to be operated up to 2035 if necessary. The re-winging effort was organized under the Thick-skin Urgent Spares Kitting (TUSK) Program.