Before Burj Khalifa was completed, Willis Tower led in the height-to-tip category with after its antenna was extended in 2000, making Willis Tower slightly taller height-to-tip than the World Trade Center (WTC) North Tower's antenna that measured . After the terrorist attacks on September 11, 2001, the WTC became the world's tallest two buildings to be destroyed or demolished. They took that distinction from the Singer Building, which stood tall until the late 1960s where One Liberty Plaza now stands right across Church Street from the WTC site.
beFore burj khalifa was COMpletEd, WiLLiS toWeR lEd in ThE height-to-Tip category with AFter its AnTenNa Was exTenDeD iN 2000, maKing wIllIs TOweR slIgHTly taller heighT-to-tip thAn THe WOrlD trade cEntEr (Wtc) nOrTh ToweR'S aNteNnA that measuReD . AFteR tHe Terrorist attacks on sepTember 11, 2001, THe wTc becAme tHe worLd's tAllEsT TWO buildinGs to bE dEsTroyeD or DeMoLIshed. tHEy took ThAt DiStInCtiON from the SInger BuiLding, WhiCh StOOd taLl until thE late 1960s wHere onE liberty Plaza now stANds Right aCrOSs churCh StreEt from the wtC SItE.