Defense News reports that "the US Air Force will include both the U-2 spy plane and Global Hawk unmanned system in their FY16 budget request, but will once again ask to retire the A-10 Warthog, sources tell Defense News."
"Both the Global Hawk and the U-2 perform the high-altitude intelligence, surveillance and reconnaissance (ISR) mission, and for several years the Air Force attempted to retire the Global Hawk in favor of the U-2, claiming the older platform was still cheaper and had greater capabilities than the Global Hawk."
"In its FY15 request, the Air Force flipped, arguing that per-flying hour costs had come down enough on the Global Hawk that the unmanned system was now the cheaper option. The service claimed that retiring the U-2 could save $2.2 billion. Those savings dropped dramatically, however, when factoring in the costs for needed upgrades to the Global Hawk that would allow it to fill current U-2 capabilities."