As Sears continued to offer optimistic growth projections, the height of the proposed tower also increased. Under Chicago's relatively lax zoning laws, the site could theoretically accommodate a 300-story building with . In practice, most potential tenants did not want excessively high offices. Additionally, the Federal Aviation Administration (FAA) restricted the height of structures in the area to protect air traffic. FAA officials publicly denied that they had imposed a height limit; however, the area's minimum safe altitude would need to be raised by if the building was just taller. Plans for the tower were announced on July 27, 1970. The building would contain 109 stories as measured from Wacker Drive and 110 stories as measured from Franklin Street. This would make Sears's new tower the tallest in the world, as measured by roof height, although New York City's under-construction World Trade Center Twin Towers would have a taller antenna. Although the Sears Tower would contain of space, only about would be used as offices.
as sears continued tO oFFer OpTiMIstic grOwTH PrOjECTions, the HeiGHt of thE proposed towEr Also INcrEased. uNder chicago's rElATivelY lax zoninG laws, the Site CoULD TheOrETically AccommodatE a 300-stOry buIlding WiTH . in practIce, mOSt PotentiAl tEnantS DiD Not wAnT exceSsively higH offIces. aDditionaLly, THe feDerAl AVIAtiOn admiNistrAtion (faA) resTricteD the HeIgHt oF stRuCTUrES In thE Area to proTEct aiR tRafFIc. fAa officIaLs PubLIcly denied thAt tHEy had imposed a heigHt limiT; howEver, ThE aRea'S MinimUM sAfe altitude woUld NeEd to be raiSed by If The bUildinG was jUsT tallEr. plaNS FoR tHe tOwer were AnnouncEd on jULY 27, 1970. tHe buiLdIng woulD conTaIn 109 stOrIes as MeasURED FROm wAckeR drIve anD 110 stoRIes As mEasUReD From frAnkLin STreEt. thIS would make seArs's neW tower tHe tallEst in thE WORld, As meaSurEd By rOOF HeiGht, Although nEw yORk CItY's undeR-conSTRuction woRLd traDe cENter tWIn towers wOUld haVe a tAller anTenna. aLthOugH The seARs tower wOulD conTAIN of SPAce, onlY AbouT wOUld be USeD aS offIcEs.