 Northrop Grumman is promoting schemes where several Global Hawks with different but complementary payloads could be used to perform a single mission.Current USAF plans project 40 to 45 Global Hawks in service by 2010 and 78 in service by 2020, with 40 carrying electro-optic payloads and the other 38 carrying SIGINT payloads.The Air Force expects to retire their aging U-2 reconnaissance aircraft no later than 2011, and are hesitantly considering the Global Hawk as the replacement.