620 ILCS 25/24
Any person desiring to erect any structure, or increase the height of any structure, or permit the growth of any tree, or otherwise use his property in violation of airport zoning regulations adopted under this Act, may apply to the Department, when it has prescribed said regulations, and in other cases, to the Board of Appeals, for a variance from the zoning regulations in question. Such variances shall be allowed where a literal application or enforcement of the regulations would result in practical difficulty or unnecessary hardship and the relief granted would not be contrary to the public interest but do substantial justice and be in accordance with the spirit of the regulations and this Act; Provided, That any variance may be allowed subject to any reasonable conditions that the Department or the Board of Appeals, as the case may be, may deem necessary to effectuate the purposes of this Act. Nothing in this section authorizes the allowance of any variation which will conflict with any zoning ordinance or regulation of any political subdivision, except such as is adopted exclusively for airport zoning.
620 ILCS 25/24