In 2009, Secretary of Defense Robert Gates announced a significant reshaping of the Pentagon’s Budget. Gates announced that the Missile Defense Agency’s budget would be cut by $1.4 billion and programs under development would be cancelled including a second Air Born Laser prototype aircraft and the Multiple Kill Vehicle. The 2010 Ballistic Missile Defense Review outlined the rationale for cancelling these programs:
The President has made clear that the United States will move forward with missile defenses that are affordable, proven, and responsive to the threat. This primarily means that the Department of Defense will realign spending away from defenses planned to rely on currently immature technology, away from technologies that require unrealistic concepts of operations in order to be effective, and away from technologies intended to defeat adversarial missile threats that do not exist and are not expected to evolve in the near to midterm. These considerations led to the decisions to terminate both the Multiple Kill Vehicle and Kinetic Energy Interceptor programs and to shift the Airborne Laser to a technology demonstration program in the FY 2010 budget. 
 Robert Gates,“Defense Budget Recommendation Statement (Arlington, VA),” The Department of Defense, April 6, 2009, Accessed November 5, 2014. http://www.defense.gov/speeches/speech.aspx?speechid=1341.
 “Ballistic Missile Defense Review” The Department of Defense, February 2010, Accessed November 5, 2014, http://www.defense.gov/bmdr/docs/BMDR%20as%20of%2026JAN10%200630_for%20web.pdf.
Below are some discontinued missile defense programs: