620 ILCS 5/74
In exercising its powers and performing its functions under the laws of this State pertaining to aeronautics, when it is necessary for the use and benefit of the public, pursuant to such laws, that private property be taken or damaged or entry be made on private property, for the purpose of constructing and installing any airport, restricted landing area or other air navigation facility, including buildings, structures and other improvements in connection therewith, the Department in the name of the State, within the limitations of available appropriations, shall have the right to purchase the necessary land, rights in land, or easements, including avigation easements, from the owner thereof and purchase from the owner the right of entry, or if compensation therefor cannot be agreed upon between the Department and the owner, to have just compensation ascertained and to acquire and pay for such property, land, easement or right of entry, in the manner provided for the exercise of the right of eminent domain under the Eminent Domain Act . When the Department, in the name of the State, files a petition to condemn any private property, rights in land, or easement, as herein provided, the Department may enter upon the land and premises, and the buildings or structures located thereon, notwithstanding that the damage or compensation in connection with such condemnation has not theretofore been determined and paid.
620 ILCS 5/74