Statistically speaking, civilian casualties were lighter than any other conflict involving modern mass airpower.[3] From the beginning of Operation Allied Force, NATO pledged to minimise civilian casualties. Consideration of civilian casualties was incorporated into NATO's planning and targeting process. Targets were "looked at in terms of their military significance in relation to the collateral damage or the unintended consequence that might be there", according to General Henry Shelton, Chairman of the Joint Chiefs of Staff.[4] Critics of the campaign have suggested that incidents were the inevitable result of NATO's policy of restricting its pilots to bombing from 15,000 feet or above for the sake of avoiding NATO deaths.[5]