Boeing WC - 135 Constant Phoenix The WC - 135 Constant Phoenix is a special purpose aircraft derived from the Boeing C - 135 and used by the United States Air Force . Its mission is to collect samples from the atmosphere for the purpose of detecting and identifying nuclear explosion s . It is also informally referred to as the " weather bird " or " the sniffer " by workers on the program . Mission . The WC - 135C and WC - 135W Constant Phoenix atmospheric collection aircraft support national level intelligence consumers by collecting particulate debris and gaseous effluents from accessible regions of the atmosphere in support of the Limited Nuclear Test Ban Treaty of 1963 . Features . The WC - 135W ( tail number 61 - 2667 ) is a modified C - 135B . The WC - 135C ( tail number 62 - 3582 ) is an extensively modified former EC - 135C Looking Glass aircraft . The Constant Phoenix ’ s modifications are primarily related to the aircraft ' s on - board atmospheric collection suite , which allows the mission crew to detect radioactive debris " clouds " in real time . The aircraft is equipped with external flow - through devices to collect particulates on filter paper and a compressor system for whole air samples collected in high - pressure holding spheres . The interior seats 33 people , including the cockpit crew , maintenance personnel , and special equipment operators from the Air Force Technical Applications Center . On operational sorties , the crew is minimized to just pilots , navigator , and special equipment operators , to reduce radiation exposure to mission - essential personnel only . Vela Incident . WC - 135B aircraft flew 25 sorties in 1979 to try to ascertain if a double flash in the south Atlantic that was detected by a Vela satellite was a nuclear weapons test , however the result was inconclusive . Pakistan & India . The Constant Phoenix aircraft was used to gather information on the nuclear tests conducted by Pakistan and India in 1998 . North Korea . On Friday 6 October 2006 Japan ' s Kyodo News agency reported that a US military aircraft , equipped to detect radiation from a nuclear test , took off from southern Japan . This was believed to be part of US efforts to prepare to monitor a North Korean nuclear test . On Monday 9 October 2006 North Korea ' s official Korean Central News Agency ( KCNA ) reported that the country had performed a successful underground nuclear test . On October 13 , 2006 CNN reported : " The U . S . Air Force flew a WC - 135 Constant Phoenix atmospheric collection aircraft on Tuesday to collect air samples from the region . A preliminary analysis of air samples from North Korea shows " radioactive debris consistent with a North Korea nuclear test , " according to a statement from the office of the top U . S . intelligence official . The statement , from the office of Director of National Intelligence John Negroponte , was sent to Capitol Hill but not released publicly . CNN obtained it from a congressional source . The national intelligence office statement said the air samples were collected Wednesday , and analysis found debris that would be consistent with a nuclear test " in the vicinity of Punggye " on Monday . The South Korean Defense Ministry told CNN that the United States has informed it that radioactivity has been detected . " The aircraft was based at Offutt AFB , and was sent to Kadena AB on Okinawa to operate during the sampling missions . On June 17 , 2009 JoongAng Daily reported , in reference to a purported May 25 nuclear test by North Korea : " The U . S . Air Force twice dispatched a special reconnaissance jet , the WC - 135 Constant Phoenix from Kadena Air Base in Okinawa , Japan , to collect air samples . " On November 23 , 2010 Sankei Shimbun reported that a WC - 135 had been moved to Kadena Air Base in September 2010 , in anticipation of a North Korean nuclear test . On January 31 , 2013 the WC - 135W was reported to be conducting surveillance flights out of Kadena Air Base in anticipation of another North Korean nuclear test . Japan . On March 17 , 2011 CNN reported WC - 135W had been deployed from Offutt Air Force Base to assist in detecting radioactive materials in the atmosphere around Japan , monitoring radiation released from the Fukushima I Nuclear Power Plant caused by the magnitude 9 . 0 earthquake and subsequent tsunami of March 11 , 2011 . the aircraft have been assigned to Eielson Air Force Base temporarily .