551st Strategic Missile Squadron The 551st Strategic Missile Squadron ( 551 SMS ) is an inactive United States Air Force unit . It was last assigned to the 98th Strategic Aerospace Wing , stationed at Lincoln AFB , Nebraska The 551 SMS was equipped with the SM - 65F Atlas Intercontinental ballistic missile ( ICBM ) , with a mission of nuclear deterrence . The squadron was inacivated as part of the phaseout of the Atlas ICBM on 25 June 1965 . History . World War II . Activated in late 1942 as a B - 17 Flying Fortress heavy bomb squadron , trained under Second Air Force . Deployed to England in the European Theater of Operations ( ETO ) during June 1943 , assigned to VIII Bomber Command as a strategic bombardment squadron . Participated in the air offensive over Nazi Germany and Occupied Europe until German capitulation in May 1945 . Personnel demobilized in England and returned to the United States ; squadron reassigned to Second Air Force and was programmed to be re - equipped with B - 29 Superfortress es for deployment to Pacific Theater . Japanese capitulation led to units inactivation in September 1945 , being neither manned or equipped . Effective 15 September 1947 , the squadron was activated at Selfridge Field , Michigan . Having been allotted to the organized reserves , with assignment to Second Air Force , Air Defense Command , it was redesigned as a very heavy bombardment unit on 25 August . In August 1948 , the squadron was assigned to the Tenth Air Force , which in December , became a part of the Continental Air Command . On 1 December 1948 it was again reassigned to Air Defense Command where it remained on reserve service until being inactivated on 27 June 1949 due to budget restrictions . Intercontinental Ballistic Missile Squadron . Reactivated in 1960 as a Strategic Air Command SM - 65F Atlas ICBM launch squadron , stationed at Lincoln AFB , Nebraska and assigned to the 818th Air ( later Strategic Aerospace ) Division on 1 April 1961 . The squadron was assigned twelve missiles , based in a 1 x 12 configuration : twelve independent widely dispersed launch sites comprised the missile squadron . The Atlas F was the final and most advanced version of the Atlas ICBM and was stored in a vertical position inside underground concrete and steel silos . When stored , the Atlas F sat atop an elevator . If a missile was placed on alert , it was fueled with RP - 1 ( kerosene ) liquid fuel , which could be stored inside the missile for extended periods . If a decision was made to launch the missile , the missile was raised to the surface and the liquid oxygen tank was filled . The launch would occur shortly after completion of this process . ( see below for site details ) . The exposure on the surface that this procedure entailed was the great weakness of the Atlas F . It was exposed and vulnerable during this time . The Titan II and Minuteman missiles could be launched from within their silos , thereby eliminating this vulnerability . Also , since the Titan did not use a cryogenic fuel or oxydizer , and the Minuteman was a solid fuel rocket , they could be stored fully fueled and ready to launch within a very few minutes . The 551st SMS operated twelve launch silos ; one missile at each site . The missiles were retired and removed in early 1965 in favor of the more advanced LGM - 25C Titan II ; squadron was inactivated on 25 June 1965 . Missile sites were later sold off to private ownership after demilitarization .