"(B) Limitations. The 
      Secretary shall not authorize the conversion of any of following 
      facilities or functions of the air traffic control system, as defined in 
      section 40102, to a private entity or a public entity other than the 
      United States Government:
      
      "(i) A facility controlled by the Federal Aviation Administration.
      "(ii) Operations performed, on the date of enactment of this subparagraph, 
      by Federal employees at a facility controlled by the Federal Aviation 
      Administration.
      "(iii) Maintenance, engineering, or oversight functions performed, on or 
      after the date of enactment of this subparagraph, at a facility controlled 
      by the Federal Aviation Administration.
      
      "(C) Applicability of limitations.--
      
      "(i) Contract tower 
      program.-- Subparagraphs (B)(i) and (B)(ii) shall not apply to a 
      Federal Aviation Administration airport traffic control tower operated 
      under the contract tower program on the date of enactment of this 
      subparagraph.
      (ii) Existing maintenance and engineering agreements.-- 
      Subparagraphs (B)(iii) shall not apply to the renewal or replacement of a 
      maintenance or engineering agreement in effect on the date of enactment of 
      this subparagraph.".