The 2006 Quadrennial Defense Review (QDR), directed the Air Force to develop a new long-range precision strike capability by 2018. USAF officials identified the new bomber as having top-end low-observability characteristics with the ability to loiter for hours over the battlefield area and respond to threats as they appear. Major General David E Clary, ACC vice-commander, summed it up by saying the new bomber would "penetrate and persist". Deployment of cruise missiles was another issue for the new bomber. The B-52 is the only aircraft currently in the Air Force inventory allowed under strategic nuclear arms reduction treaty to be armed with nuclear cruise missiles. Major consideration was paid to operation readiness and flexibility. In 2006, the program expected that a prototype could be flying as early as 2009. In September 2007, several Air Force generals stressed that it was still their plan to field the bomber by 2018. In order to meet the tight schedule, the Air Force would initially pursue a basic model then improves its capabilities subsequently.